Flow Sensor for Ventilation

ABSTRACT

A flow sensor system for ventilation treatment comprises a flow conduit configured to allow gas flow between a first region and a second region, the flow conduit defining a lumen for the gas flow; a flow restrictor disposed within the lumen of the flow conduit between the first region and the second region; a first absolute pressure sensor disposed adjacent to the first region of the flow conduit and configured to measure a pressure of the gas flow at the first region of the flow conduit; and a second absolute pressure sensor disposed adjacent to the second region of the flow conduit and configured to measure pressure of the gas flow at the second region of the flow conduit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from U.S. Provisional PatentApplication No. 62/309,784, filed on Mar. 17, 2016, which isincorporated herein by reference in its entirety.

BACKGROUND

Field

The present disclosure is related to a flow sensor device for use inproviding ventilation therapy to a patient, for example, flow sensordevices that measure flow rate and/or volume of gas delivered to apatient during ventilation therapy which may be useful to providefeedback to an operator and/or system to adjust the delivery of gas tothe patient based on the measured flow rate and/or volume of gas.

Description of Related Art

Ventilation systems and assemblies are commonly used in the art todeliver gas, such as air or oxygen, to a patient as part of an ongoingtreatment or medical emergency when the patient requires assistance inbreathing. Commonly during medical emergencies, an emergency medicaltechnician (EMT), nurse, or doctor manually ventilates the patient usinga manually actuatable bag ventilator system. During cardiac arrest,over-bagging of the patient is common and reduces the patient's chancesof survival because rescuers may be prone to hyper-ventilate the patientbeyond recommended levels.

Prior solutions to this problem have involved providing the rescuer witha measurement of the patient's end-tidal CO₂ (ETCO₂) or SpO₂ or toinstruct the rescuer to listen to lung sounds and count the respiratoryrate manually. These solutions offer several drawbacks. For instance,ETCO₂ measurements are reflective of several factors, including thepatient's metabolism, circulation and ventilation, and do notnecessarily reflect the flow rate or volume of gas being delivered tothe patient to give the rescuer an indication that the ventilationtherapy is being performed correctly. In addition, there is asignificant time delay between when a patient may experience reducedventilation and when the SpO₂ of the patient is noticeably affected.Also, the rescuer may not be able to adequately detect the patient'srespiration by ear or may be overburdened with the number of tasksnecessary for resuscitation, and so might not be able to manually countthe patient's respirations.

Typical flow sensors associated with a manual or automatic ventilationsystem commonly utilize a single differential pressure sensor, which islarge and expensive. Such flow sensors may be prone to the accumulationof moisture, fluid, and debris on the sensor or within the sensorsystem, which disrupts operation of the sensor. Conventional flowsensors may also require substantial tubing to carry air to a largersystem or monitor, which may be cumbersome, for example, in emergencysituations where kinking of tubes and extra lines connected to thepatient may increase risk of further complications. Accordingly, suchsensors are typically only used in a hospital or clinical setting wherethey can be regularly maintained and sterilized and where transportationof the sensor is not an issue. Use of such sensors in emergency medicalsettings, particularly in the field, is limited.

SUMMARY

According to one particular aspect of the present disclosure, a flowsensor system for assisting resuscitative treatment is provided. Theflow sensor system comprises a flow conduit configured to be placed in apatient airway and having a lumen that accommodates gas flow between afirst region and a second region; a flow restrictor disposed within thelumen of the flow conduit between the first region and the secondregion; and at least one pressure sensor configured to measure gaspressure of at least one of the first region and the second region ofthe flow conduit. A sensitive region of the flow sensor system exhibitsa greater level of hydrophobicity than a neighboring region adjacent tothe sensitive region.

In one example, the sensitive region includes at least a portion of theflow restrictor. Or, the sensitive region may include a portion of theflow conduit configured to accommodate substantially laminar flowthrough the lumen. Alternatively, the sensitive region may include atleast a portion of a barrier that protects or separates the pressuresensor(s) from the lumen of the flow conduit. The neighboring region mayinclude a reservoir configured to collect water arising from gas flowingthrough the lumen. The neighboring region may be configured to wick awaywater from the sensitive region.

In one example, the at least one pressure sensor includes a firstabsolute pressure sensor configured to measure gas pressure at the firstregion of the flow conduit and a second absolute pressure sensorconfigured to measure gas pressure at the second region of the flowconduit.

In one example, the at least one pressure sensor includes a differentialpressure sensor configured to measure differential gas pressure betweenthe first and second regions of the flow conduit.

In one example, the flow sensor system further comprises a processor incommunication with the at least one pressure sensor, the processor beingconfigured to generate a signal for determining at least one of a peakinspiratory pressure, a flow rate and a volume of gas flowing throughthe lumen of the flow conduit based on the pressure measurements in thefirst and second regions of the flow conduit. The processor may beconfigured to output signals relating to the measured gas pressure atthe first and second regions of the flow conduit. The processor may beconfigured to send a signal displaying physiological data of the patient(e.g., vitals information) and resuscitative information to a user(e.g., feedback to adjust the gas flow through the lumen of the flowconduit, or other instructions) based on at least one of peakinspiratory pressure, the determined flow rate and the determined volumeof gas flowing through the lumen. The resuscitative information mayinclude at least one of feedback for instructing a user to adjustplacement of an intubation tube, an alert that overventilation hasoccurred, a countdown of at least one of a number of chest compressionsand time until a subsequent ventilation is to be applied, a number ofchest compressions applied based on at least one of the first and secondsignals, a determination of whether a detected breath is due tospontaneous breathing, manually applied ventilation or automaticallyapplied ventilation, an indication of whether ROSC (Return ofSpontaneous Circulation) may have occurred, and at least one of thedetermined peak inspiratory pressure, flow rate and volume of gasflowing through the lumen of the flow conduit, or other instructiveinformation. The physiological data may include at least one of ECG(Electrocardiography) data, SpO2 data, EtCO2 data, blood pressure, heartrate, temperature, SmO2 and muscle pH of the patient, or otherphysiological information. The processor may be configured to generate asignal for compensating for effects of altitude and/or temperature indetermining the at least one of the flow rate and the volume of gasflowing through the lumen of the flow conduit.

In one example, the at least one pressure sensor is further configuredto measure a temperature of gas flowing through the lumen of the flowconduit. The processor may be configured to generate a signal fordetermining at least one of the flow rate, a direction of flow andvolume of gas flowing through the lumen based on the pressuremeasurements and the temperature measurement.

In one example, the flow sensor system further comprises a connectorremovably coupled with the flow conduit, the connector being configuredto place the at least one pressure sensor in communication with theprocessor. The connector may be configured to be rotatably coupled tothe flow conduit while maintaining electrical communication between theat least one pressure sensor and the processor. The connector maycomprise the at least one pressure sensor. The connector may comprisethe processor. The connector may be configured to provide at least oneof audio feedback, visual feedback and haptic feedback to adjust the gasflow through the lumen of the flow conduit based on at least one of thedetermined flow rate and volume of gas flowing through the lumen.

In one example, the flow restrictor is configured to interrupt the flowof gas through the lumen to create a pressure drop in the lumen betweenthe first region and the second region and the processor is configuredto determine the pressure drop based on the pressure measurements of theat least one pressure sensor and to determine at least one of the flowrate, a direction of flow and volume of gas flowing through the lumenbased on the determined pressure drop. The processor may comprise amemory that incorporates a flow pressure look up table comparingmeasured pressure drops with calculated flow rates and/or volumes andthe processor determines the flow rate and/or volume of the gas flowingthrough the lumen by referencing the flow pressure look up table. Theprocessor may be configured to generate a signal for outputting thedetermined peak inspiratory pressure, flow rate and/or volume of gasflowing through the flow conduit.

In one example, the flow sensor system further comprises at least oneadditional sensor configured to measure at least one of the following: atemperature of the gas flowing through the flow conduit, a concentrationof gas flowing through the conduit, a humidity of the gas flowingthrough the conduit, and an ambient atmospheric pressure.

In one example, the processor is configured to generate a signal fordetermining at least one of the flow rate, a direction of flow andvolume of gas flowing through the lumen based on the pressuremeasurements and at least one of the following: the temperaturemeasurement, the humidity measurement, and the ambient atmosphericpressure measurement. The processor may be configured to generate asignal for detecting whether a leak exists in the flow conduit. Thesystem may be configured to be placed in communication with a mask opento ambient conditions.

In one example, the system is configured to be placed in communicationwith a ventilation assembly for delivering gas through the lumen of theflow conduit. The ventilation assembly may comprise a manual bagventilation system. The ventilation assembly may comprise an automatedventilation system.

In one example, the at least one pressure sensor is amicroelectromechanical systems (MEMS) device.

In one example, the flow sensor system further comprises a circuit boarddisposed on the flow conduit, the at least one pressure sensor beingconnected to the circuit board. The circuit board may comprise at leastone heating element configured to be energized to prevent or limit fluidaccumulation near the at least one pressure sensor.

In one example, the flow restrictor is configured to create a pressuredrop in the flow conduit between the first region and the second regionthat is substantially linearly variable based upon the flow of gasthrough the lumen. The flow restrictor may comprise a body comprising ahydrophobic material configured to be disposed in the lumen of the flowconduit, the body comprising: an outer portion surrounding an openingand at least one flap disposed in the opening. The at least one flap iscoupled to the outer portion at a side of the opening. The at least oneflap is configured to deflect from the opening due to gas flow throughthe flow restrictor. The sensitive region may include the at least oneflap and the neighboring region includes the outer portion. Thesensitive region may include at least a portion of the body of the flowrestrictor and the neighboring region includes at least a portion of theflow conduit. The at least one flap may have a surface area smaller thana projected area of the opening forming a gap in the body of the flowrestrictor when the at least one flap is in a non-deflected positionwithin the opening. The at least one flap may be shaped such that adistance is provided by the gap between the outer portion and the atleast one flap is non-uniform. The at least one flap may be shaped suchthat a distance provided by the gap between the outer portion and the atleast one flap is substantially uniform. An amount of deflection of theat least one flap from the opening is variable based upon the flow ofgas through the lumen to create the linearly variable pressure drop. Theouter portion of the body of the flow restrictor may comprise amechanical reinforcement. The mechanical reinforcement may comprise atleast one laminate layer applied to the outer portion. The mechanicalreinforcement may comprise a stiffener coating. The body may be formedfrom at least one of polytetrafluoroethylene and polyethyleneterephthalate.

In one example, the flow conduit comprises a body extending from a firstend to a second end, the body of the flow conduit having a hollowinterior defining the lumen for the gas flow. The body of the flowconduit may comprise at least one chamber configured to house andsupport the at least one pressure sensor. The at least one chamber mayinclude a first chamber and a second chamber in separate fluidcommunication with the lumen via respective openings defined in the bodyof the flow conduit.

In one example, the flow sensor system further comprises at least onebarrier for protecting the at least one chamber. The at least onebarrier may be configured to allow passage of gas and obstruct passageof moisture and debris therethrough. The at least one barrier maycomprise at least two barriers, each of the at least two barriersconfigured to protect a respective one of two chambers from moisture anddebris. The at least one barrier may comprise a breathable hydrophobicmaterial. The breathable hydrophobic material may comprise at least oneof the following: polytetrafluoroethylene, expandedpolytetrafluoroethylene, and woven fabric. The at least one barrier maybe coated with a breathable hydrophobic material. The breathablehydrophobic material may comprise at least one of the following:polytetrafluoroethylene and expanded polytetrafluoroethylene.

In one example, the at least one chamber is sealed from fluidcommunication with the lumen. The at least one barrier may include atleast one diaphragm membrane configured to prevent passage of gas,moisture and debris therethrough. The at least one diaphragm membranemay be configured to equalize pressure between the lumen and thechambers. The at least one diaphragm membrane may include a texturedsurface that allows the at least one diaphragm membrane to flex back andforth. The at least one diaphragm membrane may include at least onerolling diaphragm configuration.

In one example, the body comprises two pieces of molded thermoplasticmaterial that are ultrasonically welded. In another example, pieces ofthe body may be snap fit together. The two pieces may define arespective one of the first region and the second region of the flowconduit. Alternatively, the body may be formed as a single molded part.

In one example, the lumen of the flow conduit is shaped so as to besubstantially symmetric about a longitudinal axis of the flow conduit.

According to another particular aspect of the present disclosure, a flowsensor system is provided. The flow sensor system comprises a flowconduit configured to be placed in a patient airway and having a lumenthat accommodates gas flow between a first region and a second region;at least one sensor configured to measure gas flow information at thefirst region and/or the second region of the flow conduit; at least onechamber configured to house and support the at least one sensor; and atleast one barrier separating the lumen through the gas flows and the atleast one chamber. A sensitive region of the flow sensor system exhibitsa greater level of hydrophobicity than a neighboring region adjacent tothe sensitive region.

In one example, the at least one barrier includes the sensitive regionand a portion of the flow conduit adjacent the flow restrictor includesthe neighboring region. The at least one barrier may be a membraneconfigured to allow passage of gas and obstruct passage of moisture anddebris therethrough. The chamber may be in fluid communication with thelumen via an opening defined in the body of the flow conduit.

In one example, the body of the flow conduit has two chambers definedtherein configured to house and support respective sensors adjacent toand in communication with the lumen. Each of the two chambers may be inseparate fluid communication with the lumen via an opening defined inthe body of the flow conduit.

In one example, the at least one barrier comprises at least twobarriers, each of the at least two barriers separating a respective oneof the two chambers and the lumen through which gas flows.

In one example, the at least one barrier comprises a breathablehydrophobic material. The breathable hydrophobic material may compriseat least one of the following: polytetrafluoroethylene, expandedpolytetrafluoroethylene, and woven fabric.

In one example, the at least one barrier is coated with a breathablehydrophobic material. The breathable hydrophobic material may compriseat least one of the following: polytetrafluoroethylene and expandedpolytetrafluoroethylene.

In one example, the at least one barrier seals the at least one chamberoff from the lumen. The at least one barrier may be at least onediaphragm membrane configured to prevent passage of gas, moisture anddebris therethrough. The at least one diaphragm membrane may beconfigured to equalize pressure between the lumen and the at least onechamber. The at least one diaphragm membrane may include a texturedsurface that allows the at least one diaphragm membrane to flex back andforth. The at least one diaphragm membrane may include at least onerolling diaphragm configuration.

In one example, the body comprises two pieces of molded thermoplasticmaterial that are ultrasonically welded. The two pieces may define arespective one of the first region and the second region of the flowconduit. The lumen of the flow conduit may be shaped so as to besubstantially symmetric about a longitudinal axis of the flow conduit.

In one example, the flow sensor system further comprises at least oneheater configured to prevent or limit fluid accumulation to adjacent theat least one barrier.

In one example, the body of the flow conduit comprises at least onetapered region adapted to funnel gas from the at least one barriertoward the at least one chamber. The at least one barrier may bedisposed between the lumen and the at least one tapered region. The bodymay be configured to support a flow restrictor disposed in the lumen.

In one example, the flow conduit is configured to be assembled in fluidcommunication with a ventilation assembly.

In one example, the flow sensor system further comprises at least onerim made from a hydrophilic material disposed in the flow conduit, theat least one rim being configured to draw moisture away from the atleast one chamber.

In one example, the flow sensor system further comprises a condensationelement disposed in the flow conduit, the condensation element beingconfigured to collect moisture from the gas flowing through the lumen.

According to another particular aspect of the present disclosure, a flowsensor system for assisting resuscitative treatment. The flow sensorsystem comprises a flow conduit configured to be placed in a patientairway and having a lumen that accommodates gas flow between a firstregion and a second region; a flow restrictor disposed within the lumenof the flow conduit between the first region and the second region; atleast one pressure sensor configured to measure gas pressure of at leastone of the first region and the second region of the flow conduit; andat least one heating element located adjacent to the at least onepressure sensor, the at least one heating element configured to beenergized to prevent fluid accumulation near the at least one pressuresensor.

In one example, a sensitive region of the flow sensor system exhibits agreater level of hydrophobicity than a neighboring region adjacent tothe sensitive region. The neighboring region may be configured tocollect water arising from gas flowing through the lumen.

In one example, the at least one pressure sensor includes a firstabsolute pressure sensor configured to measure gas pressure at the firstregion of the flow conduit and a second absolute pressure sensorconfigured to measure gas pressure at the second region of the flowconduit.

In one example, the at least one pressure sensor includes a differentialpressure sensor configured to measure differential gas pressure betweenthe first and second regions of the flow conduit.

In one example, the flow sensor system comprises a processor incommunication with the at least one absolute pressure sensor, theprocessor being configured to generate a signal for determining at leastone of a peak inspiratory pressure, a flow rate and a volume of gasflowing through the lumen of the flow conduit based on the pressuremeasurements in the first and second regions of the flow conduit.

In one example, the flow sensor system further comprises at least onechamber configured to house and support the at least one pressuresensor. The at least one chamber may include a first chamber and asecond chamber in separate fluid communication with the lumen viarespective openings provided by the flow conduit.

In one example, the flow sensor system further comprises at least onebarrier for protecting the at least one chamber. The at least onebarrier may be configured to allow passage of gas and obstruct passageof moisture and debris therethrough. The at least one barrier maycomprise a breathable hydrophobic material.

In one example, the at least one chamber is sealed from fluidcommunication with the lumen. The at least one barrier may include atleast one diaphragm membrane configured to prevent passage of gas,moisture and debris therethrough. The at least one diaphragm membranemay be configured to equalize pressure between the lumen and thechambers.

According to another particular aspect of the present disclosure, a flowrestrictor for a flow sensor system is provided. The flow restrictorcomprises a body comprising a hydrophobic material configured to bedisposed in a lumen of a flow conduit, the body comprising: an outerportion surrounding an opening and at least one flap disposed in theopening. The at least one flap is coupled to the outer portion at a sideof the opening. The flap is configured to deflect from the opening dueto gas flow through the flow restrictor.

In one example, the at least one flap has a surface area smaller than aprojected area of the opening forming a gap in the body of the flowrestrictor when the at least one flap is in a non-deflected positionwithin the opening. The at least one flap may be shaped such that adistance provided by the gap between the outer support portion and theat least one flap is non-uniform. The flow restrictor may be configuredto interrupt a flow of gas through a flow conduit to create a pressuredrop in the flow conduit. An amount of deflection of the at least oneflap from the opening may be variable based upon the flow of gas throughthe flow restrictor such that the pressure drop created by the flowrestrictor is substantially linearly variable.

In one example, the outer portion of the body of the flow restrictorcomprises a mechanical reinforcement. The mechanical reinforcement maycomprise at least one laminate layer applied to the outer portion. Themechanical reinforcement may comprise a stiffener coating.

In one example, wherein the body is formed from polytetrafluoroethylene.In another example, the body is formed from polyethylene terephthalate.

In one example, the at least one flap comprises a single flap having apolygonal or substantially polygonal shape. The flap may have aplurality of sides, at least one of the sides being hingedly coupled tothe outer portion. Corners of the flap defined between the sides may berounded. The opening may have a rounded rectangular shape at an endopposite to the end to which the flap is hingedly coupled and whereintwo sides of the flap are disposed opposite to respective roundedcorners of the opening such that a gap formed between the flap and theouter portion is larger at the rounded corners of the opening.

In one example, the at least one flap comprises at least onesubstantially triangular flap. The at least one flap may comprise atleast three substantially triangular flaps disposed adjacent to eachother in the opening. The at least three substantially triangular flapsmay have non-uniform shapes and sizes.

According to another particular aspect of the present disclosure, aresuscitation system for assisting ventilation is provided. The systemcomprises a flow conduit having a lumen defined therein; and a processorconfigured to: receive a first signal representing a first pressure at afirst region of the flow conduit; receive a second signal representing asecond pressure at a second region of the flow conduit; determine atleast one of peak inspiratory pressure, flow rate and volume of gasflowing through the lumen of the flow conduit based on the first andsecond signals; and output a feedback signal to adjust gas flow throughthe lumen of the flow conduit based on at least one of the determinedpeak inspiratory pressure, flow rate and volume of gas flowing throughthe lumen.

In one example, the resuscitative information includes at least one of:feedback for instructing a user to adjust gas flow through the lumen,feedback for instructing a user to adjust placement of an intubationtube, an alert that overventilation has occurred, a countdown of atleast one of a number of chest compressions and time until a subsequentventilation is to be applied, a number of chest compressions appliedbased on at least one of the first and second signals, a determinationof whether a detected breath is due to spontaneous breathing, manuallyapplied ventilation or automatically applied ventilation, an indicationof whether ROSC may have occurred, and at least one of the determinedpeak inspiratory pressure, flow rate and volume of gas flowing throughthe lumen of the flow conduit.

In one example, the physiological data includes at least one of ECGdata, SpO2 data, EtCO2 data, blood pressure, heart rate, temperature,SmO2 and muscle pH of the patient.

In one example, the system further comprises a display interface havinga first portion for displaying the physiological data and a secondportion for displaying the resuscitative information.

In one example, the feedback signal includes prompting a user toventilate according to the number of chest compressions applied and/ortime elapsed since a prior ventilation.

In one example, the feedback signal includes informing a user thatoverventilation has occurred, the overventilation being from at leastone of exceeding a threshold of peak inspiratory pressure, an excessvolume administered and an excess rate of breaths administered.

In one example, the processor is configured to determine whether gasflow through the lumen of the flow conduit is produced by a spontaneousbreath, an automated ventilation breath or a manually providedventilation breath, and the feedback signal depends on the determinedgas flow through the lumen.

In one example, the feedback resuscitative information includes at leastone of visual feedback, audio feedback and haptic feedback. The visualfeedback may include at least one of a series of LED (Light EmittingDiode) lights, a user interface display, a CPR (CardiopulmonaryResuscitation) dashboard, a ventilation dashboard and a ventilationperformance indicator.

According to another particular aspect of the present disclosure, aconnector for establishing communication with a sensor disposed within amedical device. The connector comprises a housing configured to beremovably coupled to the medical device; a plurality of signalconductors through an interior region of the housing; and a signalcontact pad having a plurality of conductive elements arranged in aconcentric pattern. The conductive elements are in electricalcommunication with the plurality of signal conducts and are configuredto be placed in electrical communication with the sensor when thehousing is removably coupled to the medical device, wherein the housingis configured to be rotatably coupled to the medical device whilemaintaining electrical communication between the conductive elements andthe sensor.

In one example, the connector further comprises a processor configuredto receive and process signals originating from the sensor.

In one example, the connector further comprises a feedback componentconfigured to provide at least one of audio feedback, visual feedbackand haptic feedback to adjust a resuscitation activity of a user.

In one example, the housing is configured to be removably coupled to aflow sensor and the conductive elements are configured to receiveinformation from the sensor related to gas flow through the flow sensor.

According to another particular aspect of the present disclosure, a flowsensor system for ventilation treatment is provided. The flow sensorsystem comprises a flow conduit configured to allow gas flow between afirst region and a second region, the flow conduit defining a lumen forthe gas flow; a flow restrictor disposed within the lumen of the flowconduit between the first region and the second region; and at least oneabsolute pressure sensor configured to measure pressure of the gas flowat at least one of the first region and the second region of the flowconduit.

According to another aspect of the present disclosure, a flow sensorsystem for assisting resuscitative treatment is provided. The flowsensor system includes a flow conduit configured to be placed in apatient airway and having a lumen that accommodates gas flow between afirst region and a second region; a flow restrictor disposed within thelumen of the flow conduit between the first region and the secondregion; at least one pressure sensor configured to measure gas pressureof at least one of the first region and the second region of the flowconduit; at least one chamber configured to house and support the atleast one pressure sensor; and at least one diaphragm membrane betweenthe lumen through which gas flows and the at least one chamber, the atleast one diaphragm membrane configured to equalize pressure between thelumen and the at least one chamber.

In one example, the at least one diaphragm membrane includes a texturedsurface that allows the at least one diaphragm membrane to flex back andforth.

In another example, the at least one diaphragm membrane includes anopening that allows for gas exchange between the lumen and the at leastone chamber.

Further details and advantages of the present disclosure will becomeclear upon reading the following detailed description in conjunctionwith the accompanying drawing figures, wherein like parts are designatedwith like reference numerals throughout.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a ventilation assembly incorporating aflow sensor system according to an embodiment of the present disclosure;

FIG. 2 is a schematic cross-sectional view of a flow sensor systemaccording to an embodiment of the present disclosure;

FIG. 3 is a schematic cross-sectional view of a flow sensor systemaccording to an embodiment of the present disclosure;

FIG. 4 is a schematic cross-sectional view of a flow sensor systemaccording to an embodiment of the present disclosure;

FIG. 5 is a schematic cross-sectional view of a flow sensor according toan embodiment of the present disclosure;

FIG. 6 is a perspective view of a flow sensor system according to anembodiment of the present disclosure;

FIG. 7 is an exploded perspective view of the flow sensor system of FIG.6;

FIG. 8 is a perspective view of a flow conduit assembly of the flowsensor system of FIG. 6;

FIG. 9(a) is a cross-sectional view of the flow conduit assembly of FIG.8;

FIG. 9(b) is an enlarged area of the flow conduit assembly shown in FIG.9(a) illustrating the regions of hydrophobicity and adjacent reservoirand hydrophilicity regions;

FIG. 10 is another cross-sectional view of the flow conduit assembly ofFIG. 8;

FIGS. 11(a) and (b) are perspective views of a first piece of the flowconduit of FIG. 8;

FIGS. 12(a) and (b) are perspective view of a second piece of the flowconduit of FIG. 8;

FIGS. 13(a) and (b) are perspective views of a barrier of the flowconduit assembly of FIG. 8;

FIGS. 13(c) and (d) are perspective cross-sectional views of a flowconduit showing the effects of accumulation within the lumen;

FIGS. 14(a) and (b) are perspective views of a circuit board of the flowconduit assembly of FIG. 8;

FIGS. 14(c) and 14(d) are perspective views of an alternative circuitboard of the flow conduit assembly of FIG. 8

FIGS. 15(a) and (b) are perspective views of a circuit board cover ofthe flow conduit assembly of FIG. 8;

FIGS. 15(c) and 15(d) are perspective views of an alternative circuitboard cover of the flow conduit assembly of FIG. 8;

FIG. 15(e) is a cross-sectional view of a region where an adapter isheld in accordance with an embodiment;

FIGS. 16(a) and (b) are perspective views of a connector of the flowsensor system of FIG. 6;

FIGS. 17(a) and (b) are exploded perspective views of the connector ofFIG. 16;

FIGS. 18(a), (b), and (c) are cross-sectional perspective viewsillustrating a connection between the connector and circuit board of theflow sensor system of FIG. 6;

FIG. 19(a) is a perspective view of a flow restrictor according to anembodiment of the present disclosure;

FIGS. 19(b) and 19(c) are perspective views of an alternative flowrestrictor according to an embodiment of the present disclosure;

FIG. 19(d) depicts a partial perspective view of a flow restrictor inaccordance with an embodiment;

FIG. 19(e) depicts a cross-sectional view of a portion of a flowrestrictor in accordance with an embodiment;

FIG. 20 (a), (b), (c), (d), (e), and (f) are front views and chartsillustrating pressure drop versus flow for several examples of a flowrestrictor according to embodiments of the present disclosure;

FIGS. 21 (a) and (b) are charts illustrating pressure drop versus flowfor several examples of a flow restrictor according to embodiments ofthe present disclosure;

FIGS. 22(a) and (b) are charts illustrating flow and temperature versustime for a ventilation system according to an embodiment of the presentdisclosure;

FIG. 23 is a chart illustrating pressure drop versus flow for a variableorifice flow restrictor and a fixed orifice flow restrictor;

FIG. 24 is a chart illustrating pressure drop versus flow at low flowrates for a variable orifice flow restrictor and a fixed orifice flowrestrictor;

FIG. 25 is a perspective view of a diaphragm membrane according to anembodiment of the present disclosure;

FIG. 26 is a perspective view of another diaphragm membrane according toan embodiment of the present disclosure;

FIG. 27 is an exploded perspective view of a flow sensor systemincorporating the diaphragm membrane of FIG. 25 according to anembodiment of the present disclosure;

FIG. 28 is a partially exploded cross-sectional perspective view of theflow sensor system of FIG. 27;

FIG. 29 is a cross-sectional perspective view of the flow sensor systemof FIG. 27;

FIG. 30 is a partially exploded cross-sectional perspective view of aflow sensor system incorporating the diaphragm membrane of FIG. 26according to an embodiment of the present disclosure;

FIG. 31 is cross-sectional perspective view of the flow sensor system ofFIG. 30;

FIG. 32 is a cross-sectional perspective view of a rolling diaphragmaccording to an embodiment of the present disclosure when subjected tolower than normal ambient atmospheric pressure;

FIG. 33 is a cross-sectional perspective view of the rolling diaphragmof FIG. 32 when subjected to normal ambient atmospheric pressure;

FIG. 34 is a cross-sectional view of a flow sensor system incorporatingthe rolling diaphragm of FIG. 32 according to an embodiment of thepresent disclosure when subjected to lower than normal ambientatmospheric pressure;

FIG. 35 is a cross-sectional view of the flow sensor system of FIG. 34when subjected to normal ambient atmospheric pressure;

FIG. 36 is a schematic illustrating the deflection of the rollingdiaphragm of FIG. 32 within the chamber housing and flow conduit of theflow sensor system of FIG. 34;

FIG. 37 is a schematic of exemplary LED displays for a flow sensorsystem according to an embodiment of the present disclosure;

FIG. 38 is a perspective cross-sectional view of a flow sensor systemaccording to an embodiment of the present disclosure;

FIG. 39 is a perspective view of a flow conduit of the flow sensorsystem of FIG. 38;

FIG. 40 is a graph that plots how flow rate changes with time as chestcompressions are applied to the patient;

FIG. 41 depicts a series of graphs that show the absolute pressure,pressure differential and flow rate detected over time by the flowsensor system for a spontaneously breathing patient;

FIG. 42 depicts a series of graphs that show the absolute pressure,pressure differential and flow rate detected over time by the flowsensor system for a patient receiving positive pressure ventilation witha ventilator;

FIG. 43 depicts a series of graphs that show the absolute pressure,pressure differential and flow rate detected over time by the flowsensor system for a patient receiving manual (bagged) ventilationbreaths;

FIG. 44 depicts a flow chart illustrating a process through which asystem may utilize information provided from the flow sensor accordingto an embodiment of the present disclosure;

FIGS. 45(a)-(c) depict exemplary display dashboards for providingfeedback according to an embodiment of the present disclosure;

FIGS. 46(a)-(c) depict exemplary display dashboards for providingfeedback according to an embodiment of the present disclosure;

FIGS. 47(a) and (b) depict exemplary display dashboards for providingfeedback according to an embodiment of the present disclosure;

FIG. 48 depicts a ventilation timer display according to an embodimentof the present disclosure;

FIGS. 49(a) and (b) depict exemplary line graphs showing expired CO2tension versus exhaled volume;

FIG. 50 depicts an exemplary graph of pressure versus volume duringmanual ventilation;

FIGS. 51-53 depict exemplary screen shots of feedback displays, each ofwhich includes additional information other than the ventilationdashboard according to different embodiments of the present disclosure;

FIGS. 54 and 55 depict graphs that show examples of the ventilationvolume over time and the ventilation rate over time, respectively;

FIGS. 56(a)-(e) depict various display graphics for providing feedbackto indicate the quality of ventilations according to an embodiment ofthe present disclosure;

FIG. 57 depicts an exploded perspective view of a flow sensor system inaccordance with an embodiment;

FIG. 58 is a cross-sectional view of the assembled flow sensor system ofFIG. 57;

FIGS. 59(a)-(b) depict a perspective view and a cross-sectional view ofa chamber insert for the flow sensor of FIG. 57;

FIG. 60 depicts an exploded perspective view of another flow sensorsystem in accordance with an embodiment;

FIG. 61 is a cross-sectional view of the assembled flow sensor system ofFIG. 60;

FIGS. 62(a)-(b) depict a perspective view and a cross-sectional view ofa chamber insert for the flow sensor of FIG. 60; and

FIGS. 63-66 depict exemplary screen shots of feedback displays accordingto various embodiments of the present disclosure.

DETAILED DESCRIPTION

For purposes of the description hereinafter, spatial orientation terms,if used, shall relate to the referenced embodiment as it is oriented inthe accompanying drawing figures or otherwise described in the followingdetailed description. However, it is to be understood that theembodiments described hereinafter may assume many alternative variationsand embodiments. It is also to be understood that the specific devicesillustrated in the accompanying drawing figures and described herein aresimply exemplary and should not be considered as limiting. As usedhereinafter, the term “substantially” is defined as “possessing whollyor largely wholly the trait that is specified.”

This document relates to a flow sensor system that may be configured foruse in combination with a ventilation system (e.g., manual and/orautomated ventilation) that is low cost but sufficiently accurate tomeasure the flow rate and/or volume of gas being delivered the patient.The flow sensor system may further be resistant to the accumulation ofmoisture, fluid and/or debris that may impact the measurements of thesensor. For example, the flow sensor system may have sensitive regionsthat are more resistant (e.g., hydrophobic, oleophobic) to suchaccumulation so that pressure and flow readings remain sufficientlyaccurate. The flow sensor system may also be relatively small andconvenient for transport on an ambulance, helicopter, etc., or forstorage an emergency room or clinic. In various embodiments, the flowsensor system, or aspects thereof, may be constructed as asingle-use/disposable assembly.

The flow sensor system determines the flow rate and/or volume of gasbeing provided to a patient by a ventilation assembly or system bymeasuring a pressure drop created by a flow restrictor between tworegions of a lumen in a flow conduit of the sensor system positionedbetween the patient and the source of gas in the ventilation assembly.The pressure drop may be determined by independently measuring thepressure of the gas in the two regions of the lumen using two absolutepressure sensors positioned adjacent to the first and second regions ofthe lumen. The absolute pressure sensors may be miniatureelectro-mechanical systems (MEMS) devices. The flow restrictor mayinclude a variable orifice flow restrictor (e.g., having a flexibleflap), or the flow restrictor may include a rigid orifice. The flowsensor system is configured to provide the operator with feedback itselfor via a remotely connected device concerning the real time measurementof breath rate, volume and/or peak inspiratory pressure (PIP) of thepatient, and may also provide the operator with alerts, for example, ifthe rate or volume is above or below the ideal thresholds or if the peakinspiratory pressures are too high, e.g., above a certain thresholdwhich may be harmful to the patient.

The flow sensor system may also provide the operator with a countdown towhen a breath should be delivered or should stop being delivered to thepatient. For instance, when ventilations are to be provided to thepatient over a particular interval of time, the system may provide acountdown (e.g., via audio, visual, haptic feedback) that indicates to arescuer how much more time is allotted during the desired interval, forexample, until a subsequent resuscitation activity (e.g., ventilationsand/or chest compressions) is to be performed. The flow sensor systemcan be used in treating a patient with ventilation therapy duringcardiac arrest, traumatic brain injury, respiratory distress, and duringpatient intubation. The flow sensor system may be used according tosystems and methods discussed in U.S. 2012/0302910, entitled “WirelessVentilator Reporting,” and U.S. Pat. No. 7,747,319, entitled “AutomatedResuscitation Device with Ventilation Sensing and Prompting,” each ofwhich is hereby incorporated by reference in its entirety.

The flow sensor system may include a number of components, as discussedfurther herein. For example, the flow sensor system may include aconduit, flow restrictor, pressure sensor(s), along with one or moreconnectors (electrical and/or mechanical), processors, user interfaces,displays and/or other components that contribute to the measurement anddetermination of flow rate, volume of flow, etc. The flow sensor systemmay further include one or more apparatuses that are configured toprovide feedback to a user or machine of how to adjust ventilation orother forms of resuscitative therapies (e.g., chest compressions,defibrillating shock, etc.) based on flow measurements obtained from theflow sensor.

In some implementations, the flow sensor system may include one or morepressure sensors, as discussed herein, for measuring differentialpressure between separate regions of the flow sensor. The pressuresensor(s) may be positioned so as to measure differential pressure inthe patient airway. For example, a small vane may be positioned betweenpressure sensing ports so that the pressure difference generated betweenthe two ports is proportional to the velocity of air flow through theconduit into or out from the patient. Knowing the cross-sectional areaof the air path through the conduit, allows the tidal volume to beestimated (using known differential pressure tidal volume measurementtechniques).

Having calculated the ventilation rate and tidal volume, it is possibleto detect whether or not the appropriate number and rate of breaths havebeen given as well as the proper amount of tidal volume. If theprocessor determines that the ventilation rate may be correct, but thetidal volume may be insufficient, a message may be generated to informthe rescuer that more air should be provided to the patient. Similarmessages may also be provided to correct for incorrect ventilation rate.

With reference to FIG. 1, a ventilation assembly is shown in accordancewith an embodiment of the present disclosure. The ventilation assemblyincorporates a flow sensor system 10 according to any one of thefollowing embodiments of the present disclosure. The assembly alsocomprises a manual bag ventilation system 12, which comprises a manualgas ventilation bag and patient mask, for delivering ventilation to apatient. The manual bag ventilation system 12 is manually operated by anoperator, such as a paramedic, nurse, or doctor, to deliver breaths of agas, such as air, to the patient in a manner known to those havingordinary skill in the art. The flow sensor system 10 and an end tidalcarbon dioxide (ETC02) sensor 11 may be disposed between the ventilationbag and the mask. The flow sensor system 10 is configured to measure atleast one of a flow rate and a volume of gas being delivered to thepatient by the manual bag ventilation system 12 and/or being exhaledfrom the patient to an exhaust. The flow sensor system 10 may beconnected to a monitor device 13 by a cable connector 14 for providingthe operator with feedback concerning the flow rate and/or volume of thegas being delivered to the patient. The feedback provided by the monitordevice 13 may be visual, audio, and/or haptic feedback. This feedbackmay allow the operator to adjust the timing and/or force of theactuations of the manual bag ventilation system 12 to deliver more orless gas to the patient, as required according to the particularventilation treatment being provided. According to an alternativeembodiment, the ventilation assembly incorporates an automatedventilation system, rather than a manual bag ventilation system. In thiscase, the flow sensor system 10 may communicate directly with acontroller of the automated ventilation system to adjust the output ofthe system. According to another alternative embodiment, the flowsensor. system 10 may incorporate a display screen, speaker, and orvibrator device so that the flow sensor system 10 itself is configuredto provide the visual, audio, and or haptic feedback to adjust thedelivery of gas to the patient.

With reference to FIG. 2, a flow sensor system 20 is shown in accordancewith an embodiment of the present disclosure. The flow sensor system 20comprises a flow conduit 21 that defines a lumen 22 allowing for thepassage of gas through the flow conduit 21 from a ventilation source,such as a manual ventilation bag or automated ventilation system, to apatient. The flow conduit 21 comprises a flow restrictor 23 that extendsinto the lumen 22. The flow restrictor 23 obstructs the flow of gasthrough the lumen 22 in order to create a pressure drop in the flow.This differential pressure created by the flow restrictor 23 can bemeasured in order to calculate the flow rate and/or volume of the gaspassing through the flow conduit 21. To that end, the flow sensor system20 comprises a first absolute pressure sensor 24 and a second absolutepressure sensor 25 in communication with the lumen 22 via openings 26defined in the flow conduit 21. According to one particular embodimentof the present disclosure, the first and second absolute pressuresensors 24, 25 are miniature electro-mechanical systems (MEMS) devicesconfigured to sense an absolute pressure within a respective region ofthe lumen 22. It is to be appreciated, however, that the first andsecond absolute pressure sensors 24, 25 may be of any type known to besuitable to those having ordinary skill in the art for independentlysensing a pressure within a region of the lumen 22.

The first and second absolute pressure sensors 24, 25 are in separatefluid communication with the lumen 22 on respective sides of the flowrestrictor 23 in order to measure the absolute pressure of the gasflowing through the lumen 22 on either side of the flow restrictor 23. Aprocessor (not expressly shown) receiving the absolute pressuremeasurements from the first and second absolute pressure sensors 24, 25can thereby calculate the pressure drop created by the flow restrictor23 from which the flow rate and/or volume of the gas flowing through theflow conduit 21 can be calculated. In various embodiments, such aprocessor that calculates flow rate, volume of flow, PIP, etc. may beprovided as part of any component of the overall medical system. Forexample, the processor may be provided as part of the disposable unit(including the flow conduit and/or other components). Or, the processormay be part of the reusable cable/connector for connecting thedisposable flow unit to a larger, integrated medical system (e.g.,defibrillator, monitor, ventilator, diagnostic device, etc.). Or, theprocessor may be a part of a larger medical system; for example,pressure signals recorded from the sensors may be transmitted from thedisposable unit through the reusable connector to a more centralcomputing device (e.g., monitor, defibrillator, administrative computingdevice, tablet, etc.) for calculating certain key features ofventilation, such as flow rate, volume, PIP, amongst others.

The first and second absolute pressure sensors 24, 25 are mounted on acircuit board 28 disposed within the flow conduit 21. A membrane 27 isdisposed between each of the openings 26 and a respective one of thefirst and second absolute pressure sensors 24, 25. The membrane 27 maybe provided as a barrier and further may comprise a breathable,hydrophobic material, such as polytetrafluoroethylene (PTFE), of thetype sold under the brand name TEFLON®, and expandedpolytetrafluoroethylene (ePTFE), of the type sold under the brand nameGORE-TEX®. Alternatively, the membrane 27 may be coated with thebreathable, hydrophobic material. The membrane 27 is configured to allowgas to pass through from the opening 26 to a respective one of the firstand second absolute pressure sensors 24, 25 but to act as a barrier toobstruct or prevent the passage of liquids and debris, such as dust,sputum, vomit, saliva, etc., from passing through to interfere with theoperation or readings of the first and second absolute pressure sensors24, 25. Alternatively, a single membrane 27 may be provided that extendsacross both openings 26 and over both pressure sensors 24, 25. A gasket29 is also provided between the circuit board 28 and the flow conduit 21around each of the first and second absolute pressure sensors 24, 25 inorder to further protect the sensors 24, 25 from outside contaminants.

The flow sensor system 20 also comprises a connector 30 that comprisesthe processor or that is connected to the processor or to an externalmonitor/feedback device′ by a cable 32, as discussed above withreference to FIG. 1. The connector 30 comprises a plurality, in thisembodiment, three contacts 31 that are configured to releasably engagethe circuit board 28 on the flow conduit 21 in order to establishelectronic communication between the connector 30 and the first andsecond absolute pressures 24, 25 such that the readings of the pressuresensors 24, 25 can be communicated to the processor and/or monitordevice. By separating the processor from the flow conduit 21, theassembly of the flow conduit 21, sensors 24, 25, and the circuit board28 can be provided as a single-use unit since the assembly can beproduced relatively inexpensively. Accordingly, it is not necessary forthe assembly components to be sterilized after use, which can be laborintensive, jeopardize functioning of the components, and may notcompletely prevent spread of infection or contaminants.

As discussed herein, the flow sensor system may include a disposableportion and reusable portion. In certain embodiments, the disposableportion of the flow sensor system includes the flow conduit, pressuresensor(s) and a circuit board, and the reusable portion of the flowsensor system includes a connector for establishing communicationbetween the pressure sensor(s)/circuit board and another medical deviceor system, such as a monitor, defibrillator, ventilator, aspirator,amongst other devices, for integrating and using information gatheredfrom the flow sensor to assist in providing resuscitative therapy.

In the illustrative embodiment shown in FIG. 2, the disposable portionof the flow sensor system 20 includes the flow conduit 21, flowrestrictor 23, membrane(s) 27, gasket(s) 29, pressure sensor(s) 24, 25and a circuit board 28, amongst other single-use components, and thereusable portion of the flow sensor system 20 includes the connector 30with contacts 31, cable 32, and other parts intended to be reusable.

With reference to FIG. 3, a flow sensor system 40 is shown in accordancewith an embodiment of the present disclosure. The flow sensor system 40comprises flow conduit 41 that defines a lumen 42 allowing for thepassage of gas through the flow conduit 41 from a ventilation source,such as a manual ventilation bag or automated ventilation system, to apatient. The flow conduit 41 comprises a flow restrictor 43 that extendsinto the lumen 42. As discussed above with reference to FIG. 2, the flowrestrictor 43 obstructs the flow of gas through the lumen 42 in order tocreate a pressure drop in the flow, which can be measured in order tocalculate a flow rate and/or volume of the gas passing through the flowconduit 41.

The flow conduit 41 comprises openings 47 defined therein that allow forcommunication between the lumen 42 and a connector 44 removablyassociated with the flow conduit 41. The connector 44 comprises a firstabsolute pressure sensor 45 and a second absolute pressure sensor 46 inseparate fluid communication via the openings 47 with respective regionsof the lumen 42 on either side of the flow restrictor 43 so that thefirst and second absolute pressure sensors 45, 46 may measure theabsolute pressure of the gas passing through the lumen 42 in therespective regions to determine the pressure drop in the flow of the gasthrough the lumen 42. According to one particular embodiment of thepresent disclosure, the first and second absolute pressure sensors 45,46 are miniature electro-mechanical systems (MEMS) devices configured tosense an absolute pressure within a respective region of the lumen 42.

The first and second absolute pressure sensors 45, 46 are mounted on acircuit board 52 and disposed within an interior of the connector 44.The circuit board 52 places the pressure sensors 45, 46 with a processorand/or a monitor device, as discussed above. The connector 44 comprisesopenings that are filled with porous barriers 50 (e.g., plates,membranes, films, etc.), which align with the openings 47 in the flowconduit 41 so that gas from the lumen 42 may pass through to thepressure sensors 45, 46.

A membrane 48 is disposed outside of each of the openings 47 so as to bedisposed between the respective opening 47 and pressure sensor 45, 46when the connector 44 is connected to the flow conduit 41. As discussedabove with reference to FIG. 2, the membrane 48 may comprise abreathable, hydrophobic material that is configured to allow gas to passthrough from the opening 47 to a respective one of the first and secondabsolute pressure sensors 45, 46 but to act as a barrier to obstruct orprevent the passage of liquids and debris, such as dust, sputum, vomit,saliva, etc., from passing through to interfere with the operation orreadings of the first and second absolute pressure sensors 45, 46.Alternatively, a single membrane 48 may be provided that extends acrossboth openings 47. A gasket 49 is provided around each of the openings 47to seal the engagement between the flow conduit 41 and the connector 44around the openings 47 and prevent contaminants outside the flow sensorsystem 40 from entering the cavity in the connector 44 containing thepressure sensors 45, 46 and from entering the lumen 42. Additionally,gaskets 51 are also provided in the connector 44 around each of thefirst and second absolute pressure sensors 45, 46 to further seal andprotect the pressure sensors 45, 46. By separating the pressure sensors45, 46 and circuit board 52 from the flow conduit 41, these componentsmay be re-used for multiple treatments. Also, the assembly of the flowconduit 41 can be provided as a single-use piece with all of theelectronics removed. As discussed herein, for certain embodiments, themembrane may exhibit a greater level of hydrophobicity than neighboringregions, for example, portions of the inner surface of the flow conduitso that water or other debris may collect away from the membrane ratherthan on the membrane itself.

As noted above, the flow sensor system may include a disposable portionand a reusable portion. For certain embodiments, the disposable portionof the flow sensor system includes the flow conduit and chamberstructures for housing the pressure sensor(s), and the reusable portionof the flow sensor system includes the pressure sensor(s), associatedcircuit board and connector cable that provides communication betweenthe pressure sensor(s)/circuit board and another medical device orsystem (e.g., monitor, defibrillator, ventilator, aspirator, etc.), forintegrating and using information gathered from the flow sensor.Accordingly, for various embodiments, the pressure sensor(s) may beprovided as part of the disposable or the reusable portion of the flowsensor system.

In the illustrative embodiment shown in FIG. 3, the disposable portionof the flow sensor system 40 includes the flow conduit 41, flowrestrictor 43, membrane(s) 48, gasket(s) 49, amongst other single-usecomponents, and the reusable portion of the flow′ sensor system 40includes the pressure sensor(s) 45, 46, circuit board 52, and otherparts intended to be reusable.

With reference to FIG. 4, a flow sensor system 60 is shown in accordancewith an embodiment of the present disclosure. The flow sensor system 60comprises a flow conduit 61 that defines a lumen 62 allowing for thepassage of gas through the flow conduit 61 from a ventilation source,such as a manual ventilation bag or automated ventilation system, to apatient. A flow restrictor 63 is disposed in the flow conduit 61 so asto extend across all or a portion of the of the lumen 62 in order toobstruct the flow of gas through the lumen 62 and create a pressure dropin the flow, which as discussed above, can be measured in order tocalculate a flow rate and/or volume of the gas passing through the flowconduit 61.

The flow restrictor 63 comprises a thin film flap made from a polyesterfilm, such as biaxially-oriented polyethylene terephthalate (BoPET) ofthe type sold under the trade name MYLAR®. The flow restrictor 63 isconfigured to be mounted within the flow conduit 61 to deflect under theflow of gas through the lumen 62. The amount of deflection of the flowrestrictor 63 varies according to the flow of gas through the lumen 62.That is to say, the flow restrictor 63 will deflect less, therebycreating a larger obstruction in the lumen 62 and a relatively largerpressure drop, at lower flow rates of gas through the lumen 62 and willdeflect more, thereby creating a smaller obstruction in the lumen 62 anda relatively smaller pressure drop, at higher flow rates of gas throughthe lumen 62. Accordingly, the flow restrictor 63 may be described asproviding a “variable orifice” in the lumen 62 for creating the pressuredrop for measuring flow. In comparison, the flow restrictor describedabove with reference to FIGS. 1 and 2 may be described as providing a“fixed orifice.” The effects of providing a flow restrictor 63, whichdeflects under flow through the lumen 62, on operation of the flowsensor system 60 in comparison to providing a stationary/fixed flowrestrictor of the type described above with reference to FIGS. 1 and 2will be described in detail below with reference to later embodiments ofthe present disclosure.

The flow sensor system 60 comprises a first absolute pressure sensor 64and a second absolute pressure sensor 64 in communication with the lumen62 via respective openings 66, 67 defined in the flow conduit 61. Asdiscussed above, the first and second absolute pressure sensors may beminiature electro-mechanical systems (MEMS) devices configured to sensean absolute pressure within a respective region of the lumen 62. Thefirst and second absolute pressure sensors 64, 65 are in separate fluidcommunication with the lumen 62 on respective sides of the flowrestrictor 63 in order to measure the absolute pressure of the gasflowing through the lumen 62 on either side of the flow restrictor 63. Aprocessor (not expressly shown) receiving the absolute pressuremeasurements from the first and second absolute pressure sensors 64, 65can thereby calculate the pressure drop created by the flow restrictor63 from which the flow rate and/or volume of the gas flowing through theflow conduit 61 can be calculated. The flow sensor system 60 mayincorporate other features of the flow sensor systems 20, 40 discussedabove such as the circuit board, membrane(s), gaskets, and connector.

In this embodiment shown in FIG. 4, the disposable portion of the flowsensor system 60 includes the flow conduit 61, flow restrictor 63,membrane(s), gasket(s), pressure sensor(s) 64, 65, amongst othersingle-use components, and the reusable portion of the flow sensorsystem (not shown in FIG. 4) includes a connector for establishingcommunication between the pressure sensor(s)/circuit board and anothermedical device or system.

With reference to FIG. 5, a flow sensor system 70 is shown in accordancewith an embodiment of the present disclosure. The flow sensor system 70comprises a flow conduit 71 that defines a lumen 72 allowing for thepassage of gas through the flow conduit 71 from a ventilation source,such as a manual ventilation bag or automated ventilation system, to apatient. A flow restrictor 80 is disposed in the flow conduit 71 so asto extend across all or a portion of the lumen 72 in order to obstructthe flow of gas through the lumen 72 between a first region 73 and asecond region 74 of the flow conduit 71 and create a pressure drop inthe flow, which as discussed above, can be measured in order tocalculate a flow rate and/or volume of the gas passing through the flowconduit 71. According to an embodiment of the present disclosure, theflow conduit 71 is made up of a first piece 83 and a second piece 84molded from a thermoplastic material, which are assembled andultrasonically welded to form the flow conduit 71. The first piece 83defines half of the lumen 72 comprising the first region 73 and thesecond piece 84 defines the other half of the lumen 72 comprising thesecond region 74. The flow restrictor 80 is disposed between the firstpiece 83 and the second piece 84. The first and second pieces 83, 84 areformed such that the lumen 72 is defined symmetrically about the middleof the flow conduit 71 and the first and second regions 73, 74 have thesame shape and volume. Such a symmetric structure of the lumen mayprovide for substantially similar flow profiles for both inspiratory andexpiratory flow directions. It can be appreciated that flow conduits inaccordance with the present disclosure are not required to be formed asseparate components such as pieces 83, 84; for example, the flow conduitmay be provided as a single unitary piece that defines the lumen throughwhich fluid flows.

The flow restrictor 80 comprises at least one thin film flap disposedwithin an opening in the restrictor 80. The flow restrictor 80 isconfigured to be mounted within the flow conduit 71 so that the flapdeflects from the opening in the flow restrictor 80 under the flow ofgas through the lumen 72. The amount of deflection of the flap variesaccording to the flow of gas through the lumen 72. The flap of the flowrestrictor 80 will deflect less, thereby creating a larger obstructionin the lumen 72 and a relatively larger pressure drop, at lower flowrates of gas through the lumen 72 and will deflect more, therebycreating a smaller obstruction in the lumen 72 and a relatively smallerpressure drop, at higher flow rates of gas through the lumen 72.Accordingly, the flow restrictor 80 may be described as providing avariable orifice in the lumen 72 for creating a pressure drop formeasuring flow. Additional details concerning the flow restrictor 80will be described below with reference to FIGS. 19(a)-21, 23, and 24.

The flow sensor system 70 comprises a first absolute pressure sensor 75and a second absolute pressure sensor 76 in communication with the lumen72 via openings 77 defined in the flow conduit 71. According to oneparticular embodiment of the present disclosure, the first and secondabsolute pressure sensors 75, 76 are miniature electro-mechanicalsystems (MEMS) devices configured to sense an absolute pressure within arespective region 73, 74 of the lumen 72. It is to be appreciated,however, that the first and second absolute pressure sensors 75, 76 maybe of any type known to be suitable to those having ordinary skill inthe art for independently sensing a pressure within a region 73, 74 ofthe lumen 72.

The first and second absolute pressure sensors 75, 76 are in separatecommunication with the lumen 72 on respective sides of the flowrestrictor 80 in order to measure the absolute pressure of the gasflowing through the lumen 72 in the respective regions 73, 74 on eitherside of the flow restrictor 80. A processor (not shown) receiving theabsolute pressure measurements from the first and second absolutepressure sensors 75, 76 can thereby calculate the pressure drop createdby the flow restrictor 80 from the which the flow rate and/or volume ofthe gas flowing through the flow conduit 71 can be calculated.

The first and second absolute pressure sensors 75, 76 are mounted on acircuit board 81 disposed on the flow conduit 71. The circuit board 81and the pressure sensors 75, 76 are arranged on the flow conduit 71 suchthat the pressure sensors 75, 76 are each disposed within a respectivechamber 79 defined in the flow conduit 71 above the respective opening77. According to one embodiment of the present disclosure, the flowconduit 71 comprises a separately molded piece in which the chambers 79and a support surface for the circuit board 81 are defined. This pieceis secured to the top of the flow conduit 71. A membrane 78 is disposedbetween each of the openings 77 and the respective chamber 79. Themembrane 78 may comprise a breathable, hydrophobic material, such aspolytetrafluoroethylene (PTFE), of the type sold under the brand nameTEFLON®, and expanded polytetrafluoroethylene (ePTFE), of the type soldunder the brand name GORE-TEX®. Alternatively, the membrane 78 may becoated with the breathable, hydrophobic material. The membrane 78 isconfigured to allow gas to pass through from the opening 77 to therespective chamber 79 in which the respective one of the first andsecond absolute pressure sensors 75, 76 is positioned and to act as abarrier to obstruct or prevent the passage of liquids and debris, suchas dust, sputum, vomit, saliva, etc., from passing through to interferewith the operation or readings of the first and second absolute pressuresensors 75, 76. Alternatively, a single membrane 78 may be provided thatextends across both openings 77 and both chambers 79. For certainembodiments, the membrane may exhibit a greater level of hydrophobicitythan regions neighboring the membrane so that water or other debris maycollect away from the membrane and not interfere with pressure/flowmeasurements.

The flow sensor system 70 also comprises a connector 82 that comprisesthe processor or that is connected to the processor or to an externalmonitor/feedback device by a cable (not shown), as discussed above. Asdiscussed above with reference to FIG. 2, the connector 82 may compriseone or more contacts that are configured to releasably engage thecircuit board 81 on the flow conduit 71 in order to establish electroniccommunication between the connector 82 and the first and second absolutepressure sensors 75, 76 such that the readings of the pressure sensors75, 76 can be communicated to the processor and/or monitor device. Byseparating the processor from the flow conduit 71, the assembly of theflow conduit 71, sensors 75, 76, and the circuit board 81 can beprovided as a single-use unit since the assembly can be producedrelatively inexpensively. Accordingly, it is not necessary for theassembly components to be sterilized after use, which can be laborintensive, jeopardize functioning of the components, and may notcompletely prevent spread of infection or contaminants.

In the embodiment shown in FIG. 5, the disposable portion of the flowsensor system 70 includes the flow conduit 71, flow restrictor 80,membrane(s) 78, gasket(s), chamber(s) 79, pressure sensor(s) 75, 76,circuit board 81, amongst other single-use components, and the reusableportion of the flow sensor system includes a connector 82 forestablishing communication between the pressure sensor(s)/circuit boardand another medical device or system.

With reference to FIGS. 6-18 a flow sensor system 100 is shown inaccordance with an embodiment of the present disclosure. The flow sensorsystem 100 comprises a flow conduit 101 that defines a lumen 102allowing for the passage of gas through the flow conduit 101 from aventilation source, such as a manual ventilation bag or automatedventilation system, to a patient. The flow conduit 101 is configured toallow gas flow between a first region 103 and a second region 104. Theflow conduit 101 comprises a body extending from a first end to a secondend of the flow conduit 101. The body has a hollow interior, whichdefines the lumen 102.

A flow restrictor 105 is disposed within the lumen 102 of the flowconduit 101 between the first region 103 and the second region 104 so asto extend across all or a portion of the lumen 102 in order to obstructthe flow of gas through the lumen between the first region 103 and thesecond region 104 and create a pressure drop in the flow, which asdiscussed above, can be measured to calculate a flow rate and/or volumeof the gas passing through the flow conduit 101.

According to an embodiment of the present disclosure, the flow conduit101 is made up of a first piece 106 and a second piece 107 molded from athermoplastic material, which are assembled and ultrasonically welded toform the flow conduit 101. The first piece 106 and the second piece 107each comprise respective assembly indentations 122, 125 defined on theends of the pieces 106, 107, as shown in FIGS. 11 and 12. The assemblyindentations 122, 125 are configured to matingly engage each other toassist in assembly of the first and second pieces 106, 107. The firstand second pieces 106, 107 may be joined by any suitable method (e.g.,fastener, welding, complementary structures that couple with oneanother) or, as discussed above, the flow conduit may be provided as asingle unitary piece defining the lumen through which fluid flows. Inthis embodiment, the first piece 106 defines half of the lumen 102comprising the first region 103 and the second piece 107 defines theother half of the lumen 102 comprising the second region 104. As shownin FIGS. 7, 9, and 10, the flow restrictor 105 is disposed between thefirst piece 106 and the second piece 107. The first and second pieces106, 107 are formed such that the lumen 102 in the first and secondregions 103, 104 is defined symmetrically about the middle of the flowconduit 101 and the first and second regions 103, 104 have the sameshape and volume. As a result, the profile of flow through the lumen isnot affected by the direction of flow, for example, whether the flow isinspiratory or expiratory. To that end, the first piece 106 of the flowconduit 101, which is formed with a connection portion 116 having alarger diameter, may comprise an interior flange 148 defined at the endof the first region 103 opposite to the flow restrictor 105 so that thefirst region 103 has the same or similar dimensions as the second region104. The lumen 102 in the first and second regions 103, 104 may also bedefined substantially symmetrically about a longitudinal axis extendingthrough the flow conduit 101 from the first end to the second end, forrelatively consistent bi-directional flow. Accordingly, the flange 148may contribute to consistent flow in either direction through the lumenof the conduit. In various embodiments, the respective outer structuresof the connection portion 116 corresponding to the first piece 106 (orsection of the fluid conduit in the case of a unitary component) and theconnection portion 124 corresponding to the second piece 107 (or sectionof the fluid conduit) may differ due to the type of fitting(s) and/ortube(s) to which the flow sensor will be connected. For example, theconnection portion 116 may be configured to couple to a ribbed fitting(e.g., for a ventilator tube or ventilation port) and the connectionportion 124 may be configured to couple with a tapered fitting thatslides along the surface thereof (e.g., over or under the surface of theconduit) to form a friction or interference type fit. It can beappreciated that the connection portions may have any appropriateconfiguration for establishing a suitable port connection with a tube orconduit.

According to one particular embodiment of the present disclosure, theflow conduit 101 has an approximate length between 5-20 cm (e.g.,approximately 10-15 cm) and the approximate maximum diameter of the flowconduit 101 in the first region 103 and the second region 104 is between2-10 cm.

With reference to FIGS. 6-12, the flow sensor system 100 is configuredto be placed in communication with a ventilation assembly for deliveringgas through the lumen 102 of the flow conduit 101, as discussed abovewith reference to FIG. 1. As discussed above, the ventilation assemblymay comprise a manual bag ventilation system and/or may comprise anautomated ventilation system. Accordingly, the flow conduit 101comprises a connection portion 116 on the first piece 106 and anotherconnection portion 124 on the second piece 107. The connection portion116 on the first piece 106 may comprise an inner diameter having alarger diameter suitable for receiving an end of a tube or passageway ofthe ventilation assembly to form a standard female connection. Theconnection portion 116 may also comprise a ribbed outer diameter to forma standard male connection with a larger tube into which the connectionportion 116 is inserted. The connection portion 124 on the second piece107 may comprise a smooth outer diameter to form a standard maleconnection within another tube or passageway of the ventilationassembly. It can be appreciated that other types of connections for theflow sensor system may be possible.

As shown in FIGS. 7, 9(a), and 10, the flow restrictor 105 comprises atleast one thin film flap disposed within an opening in the flowrestrictor 105. The flow restrictor 105 is configured to be mountedwithin the flow conduit 101 so that the flap deflects from the openingin the flow restrictor 105 under the flow of gas through the lumen 102.The amount of deflection of the flap varies according to the flow of gasthrough the lumen 102. The flap of the flow restrictor 105 will deflectless, thereby creating a larger obstruction in the lumen 102 and arelatively larger pressure drop, at lower flow rates of gas through thelumen 102 and will deflect more, thereby creating a smaller obstructionin the lumen 102 and a relatively smaller pressure drop, at higher flowrates of gas through the lumen 102. Accordingly, the flow restrictor maybe described as providing a “variable orifice” in the lumen 102 forcreating a pressure drop for measuring flow. Additional detailsconcerning the flow restrictor 105 will be described below withreference to FIGS. 19(a)-21, 23, and 24.

As shown in FIGS. 9(a)-12 and 14, the flow sensor system 100 comprises afirst absolute pressure sensor 131 disposed adjacent to the first region103 of the flow conduit 101 and a second absolute pressure sensor 132disposed adjacent to the second region 104 of the flow conduit 101. Thefirst and second absolute pressure sensors 131, 132 are configured tomeasure a pressure due to gas flow at the first and second regions 103,104 of the flow conduit 101, respectively. According to one particularembodiment of the present disclosure, the first and second absolutepressure sensors 131, 132 are miniature electro-mechanical systems(MEMS) devices configured to sense an absolute pressure within arespective region 103, 104 of the lumen 102, such as the BME 280 sensoror BMP 200 sensor manufactured by Bosch Sensortec GmbH. It is to beappreciated, however, that the first and second absolute pressuresensors 131, 132 may be of any type known to be suitable to those havingordinary skill in the art capable of independently sensing a pressurewithin a region 103, 104 of the lumen 102. Alternatively, for someembodiments, absolute pressure sensors are not necessary, as one or moredifferential pressure sensors as known to those skilled in the art maybe employed. Differential pressure sensors may be configured to measurethe difference between two pressures at separate locations, such as atregions on opposite sides of the flow restrictor.

With reference to FIGS. 7, 9(a)-12, and 14, the first and secondabsolute pressure sensors 131, 132 are in separate communication withthe lumen 102 on respective sides of the flow restrictor 105 in order tomeasure the absolute pressure of the gas flowing through the lumen 102in the respective regions 103, 104 on either side of the flow restrictor105. The first and second absolute pressure sensors 131, 132 are mountedon and connected to a circuit board 110 disposed on an upper side of theflow conduit 101. The circuit board 110 and the pressure sensors 131,132 are disposed on the flow conduit such that the first absolutepressure sensor 131 is disposed in a first chamber 114 provided in theupper surface of the first piece 106 of the flow conduit 101, and thesecond absolute pressure sensor 132 is disposed in a second chamber 123provided in the upper surface of the second piece 107 of the flowconduit 101. The chambers 114, 123 are configured to house and support arespective one of the pressure sensors 131, 132 adjacent to the lumen102 of the flow conduit 101. Each of the chambers 114, 123, and thuseach of the pressure sensors 131, 132, is in fluid communication withthe lumen 102 via an opening 119 defined in and extending through theflow conduit 101 between the lumen 102 and the chamber 114, 123.

A tapered/conical cavity 120 is formed in the interior surface of eachof the first and second pieces 106, 107 at the top of the respectivefirst and second regions 103, 104. The tapered/conical cavities 120 areconfigured to channel gas from the lumen 102, through the porous barrier108 (permitting gas but not water or debris, as discussed below), to theopenings 119 and thus to the first and second absolute pressure sensors131, 132 in the respective chambers 114, 123 while minimizing orreducing the volume of space between the lumen 102 and the pressuresensors 131, 132 such that a minimal/small amount of gas is divertedfrom the lumen 102 to obtain the pressure measurements in the regions103, 104. Hence, the cavity 120 is large enough such that the pressuresensors are exposed to a sufficient amount of gas/flow exchange betweenthe lumen of the flow conduit and the cavity. Such a configurationallows for accurate pressure measurements to be obtained while taking upa relatively small volume of space. The interior surfaces of the firstand second regions 103, 104 and the tapered/conical cavities 120 may beformed or manufactured to have a smooth finish so as to limit disruptionto the flow of gas.

According to one particular embodiment of the present disclosure, theapproximate total volume of space between the lumen 102 and each of thefirst and second absolute pressure sensors 130, 132 as defined by therespective tapered/conical cavity 120, opening 119, and chamber 114, 123is between approximately 10 mm³ and 50 mm³, or between approximately 15mm³ and 40 mm³, or 23.5 mm³, or any other appropriate volume.

In some embodiments, specific “sensitive” regions are identified thatwould result in degraded performance of pressure or flow measurementswere these “sensitive” regions to be contaminated with fluid or debris.Referring to FIGS. 2, 9(b), 29 and 34, in some embodiments, thesesensitive areas may be the area of the flow restrictor 23, 105, 150 or256, the permeable or impermeable membrane 27, 108, 220 or 352, thepressure sensors 24, 25, 131, 132, 254, 255 or 307, 308, the orifices119 connecting the pressure sensor to the lumen space, the orifice ofthe pressure sensor itself, or regions adjacent to the orifices.

In some embodiments, a sensitive region may exhibit a greater level ofhydrophobicity than regions in the immediate vicinity (e.g., neighboringregions of the flow conduit) of the sensitive region so that water orother debris may collect away from the sensitive region. Otherwise, theaccumulation of such material may affect the pressure/flow readings ofthe flow sensor system. Referring to FIG. 9(b), the inner surface of theouter portion 151 of the flow restrictor 150 may be regarded as asensitive region, since accumulation of fluid or debris on this surfacewill impair the free movement of the flap 153 which would degrade themeasurement accuracy of the sensor. By having the regions adjacent tothe sensitive regions be less hydrophobic (i.e. more hydrophilic), thefluids and the debris captured by the fluid can be wicked away from thesensitive region, to a region that collects the fluid 1005. We term thisfluid collection region, the reservoir 1006.

There may also be regions 151 b, 1007, such as on the outer portion 151of the flow restrictor 150 or on the interior of the lumen 102 near theflow restrictor 150, adjacent to the sensitive regions of the flap 153and the inner surface 151 a of the outer portion 150, that are atintermediate levels of hydrophilicity. These wicking regions 151 b, 1007act as regions which wick away moisture and fluids from the sensitiveregions 153, 151 a. In some versions, the wicking regions 151 b, 1007may incorporate surface texturing or polypropylene fibers that enhancewicking action. The relative hydrophilicities of the various wickingregions 151 b, 1007 can be adjusted relative to the sensitive regions(e.g. 151 a, 153) such that the wicking action draws the fluid into thereservoir 1006 or simply away from the sensitive regions.

The inner surface 151 a can be made more hydrophobic compared to theadjacent, more hydrophilic regions 151 b by, for instance coating theinner surface 151 b with a coating to make it more hydrophobic, ortreating the adjacent regions 151 b to make them more hydrophilic.Examples of surface treatments that increase hydrophobicity includecoating with Teflon or laminating with a thin layer of Teflon or otherknown hydrophobic material. The surface may also be treated to createwhat is currently termed “ultraphobicity” or “superhydrophobicity”,where the contact angles of a water droplet exceeds 150° and theroll-off angle/contact angle hysteresis is less than 10°. This is alsoreferred to as the Lotus effect, after the superhydrophobic leaves ofthe lotus plant. A droplet impacting on these kind of surfaces can fullyrebound like an elastic ball, or pancake. This is accomplished viamicrotexturing or nano-texturing the surface, such that the liquid onthe surface is in the Cassie-Baxter state. Embodiments of the presentdisclosure may include relevant teachings from one or more of thefollowing publications, each of which are hereby incorporated byreference in their entirety: Cassie, ABD; Baxter, S. (1944).“Wettability of Porous Surfaces”. Trans. Faraday Soc. 40: 546-551.), orin the Wenzel state where microtexturing amplifies the natural tendencyof the surface (Wenzel, R N (1936). “Resistance of Solid Surfaces toWetting by Water”. Ind. Eng. Chem. 28 (8): 988-994; Richard, Denis,Christophe Clanet, and David Quéré. “Surface phenomena: Contact time ofa bouncing drop.” Nature 417.6891 (2002): 811-811; Bird, James C., etal. “Reducing the contact time of a bouncing drop.” Nature 503.7476(2013): 385-388; and Yahua Liu, Lisa Moevius, Xinpeng Xu, Tiezheng Qian,Julia M Yeomans, Zuankai Wang. “Pancake bouncing on superhydrophobicsurfaces.” Nature Physics, 10, 515-519 (2014).

In some embodiments, the superhydrophobic region may be created viasol-gel, plasma florination, electrospinning, template method,layer-by-layer self-assembly, or other methods known to those skilled inthe art. Superhyrophobicity may also be achieved in some embodiments viaa polymerization process as described by Yuan, Chen, et al. (Yuan,Zhiqing; Chen, Hong; Zhang, Jide; Zhao, Dejian; Liu, Yuejun; Zhou,Xiaoyuan; Li, Song; Shi, Pu; et al. (2008). “Preparation andcharacterization of self-cleaning stable superhydrophobic linearlow-density polyethylene”. Science and Technology of AdvancedMaterials.), which is hereby incorporated by reference in its entirety.Using such methods, or ones similar to them, “self-cleaning” regions maybe created where dirt or other contaminants deposited on the surface areeasily washed away.

In some embodiments, the hydrophobicity may be enhanced by modifying thesurface energy of the hydrophobic regions. In some embodiments, thismodification may be achieved via lubricant-impregnated surfaces asdescribed by Smith, Dhiman, et al. (Smith, J D; Rajeev Dhiman; SushantAnand; Ernesto Reza-Garduno; Robert E. Cohen; Gareth H. McKinley; KripaK. Varanasi (2013). “Droplet mobility on lubricant-impregnatedsurfaces”. Soft Matter 19 (6): 1972-1980. See Also:http://www.rsc.org/suppdata/sm/c2/c2sm27032c/c2sm27032c.mp4.), which ishereby incorporated by reference in its entirety. In some versions, asilicone oil may be utilized; other biocompatible lubricants may also beutilized. Lubricant impregnation has been shown to be effective ataiding in the mobility of viscous fluids; this is particularlyapplicable in the case of an airway flow sensor, which is in contactwith vomit, blood, saliva and various bodily excretions during use.

DIN 55660 recommends the contact angle method for determining the SFE ofa solid. The contact angle, which reflects the degree of hydrophobicityor hydrophilicity, describes the shape of a drop on the surface: thegreater the hydrophilicity, the flatter the drop will be, resulting in asmaller contact angle. Young's equation holds that the contact angle isa function of the Surface Free Energy (SFE) of the solid, the surfacetension of the liquid, and the interfacial tension between the twophases. In order to determine the SFE and its polar and dispersecomponents, contact angles are measured using multiple liquids for whichthe interactive components of the surface tension are known. Water,which is highly polar, and diiodomethane, which is a purely dispersedliquid, are two frequently used test substances. Not only do contactangle measurements yield information on the overall surface, they alsodetect differences in wettability across a single sample. Thus,position-dependent measurements (mapping) reveal whether the surface hasbeen cleaned, activated or coated uniformly. MEASUREMENT METHODS: Thereare a number of analytical methods that characterize the surface ofplastics, and, in so doing, provide information for optimizing coatingsand adhesives (e.g.): 1) Taking optical measurements of the contactangle (drop shape analysis), static and dynamic; 2) Taking mechanicalmeasurements of the contact angle using a tensiometer; 3) Determiningsurface free energy and its polar and disperse components; 4) Measuringsurface tension of liquids; 5) Calculating adhesion and interfacialtension; 6) Measuring the roll-off angle of drops on hydrophobicsurfaces.

With reference to FIGS. 25-31, the flow sensor system 250 may includeone or more impermeable diaphragm membranes 220 disposed between theflow conduit 251 and the respective chamber 252, 253 in which acorresponding pressure sensor 254, 255 is located, for the purpose ofequalizing pressure between the flow conduit 251 and the respectivechamber 252, 253. The diaphragm membrane(s) 220 may be provided asanother type of barrier between the flow conduit 251 and the respectivechamber 252, 253. The diaphragm membrane(s) 220 may be composed of arelatively thin non-porous elastic material that is impervious to gasflow therethrough. In contrast with other examples described elsewherein this disclosure where the membrane(s) may be porous so as to allowfor gas exchange between the flow conduit 251 and the respectivepressure sensor(s) 254, 255, the diaphragm membrane(s) 220 mayadditionally form an even greater barrier, adapted to seal off gas flowto the chamber 252, 253 in which the pressure sensor 254, 255 isenclosed.

The pressure sensor 254, 255 may be permanently enclosed and, thus,protected within the chamber 252, 253 sealed by the diaphragm membrane220, provided as a barrier. The diaphragm membrane(s) 220 may further beable to flex back and forth in such a manner that the volume within therespective chamber 252, 253 varies in order to equalize pressure betweenthe flow conduit 251 and the space within the respective chamber 252,253, i.e., the diaphragm membrane(s) 220 acoustically transfers pressurebetween the flow conduit 251 and the space within the respective chamber252, 253. In this case, the chamber 252, 253 may provide sufficientspace for the diaphragm membrane(s) 220 to freely flex inward andoutward, in a manner that equalizes pressure on either side of thediaphragm membrane 220. As a result, the pressure on the flow conduitside 221 of the diaphragm membrane(s) 220 is substantially the same asthe pressure on the chamber side 222 of the diaphragm member(s) 220,providing for reliable pressure measurements on either side of the flowrestrictor 256. Chambers 252, 253 sealed with a diaphragm membrane 220and enclosing a pressure sensor 254, 255 may be a part of either thedisposable portion (including the flow conduit 251, flow restrictor 256and other such components) or the reusable portion (including the cable,connector, etc.) of the flow sensor system 250.

FIGS. 25 and 26 show various embodiments of an impermeable diaphragmmembrane 220, 225 that is relatively thin and flat, and also including apatterned structure 223, 226 that provides tolerance for the membrane220 to oscillate without affecting the equalization of pressure oneither side of the membrane 220. Accordingly, the patterned structure223, 226 of the diaphragm membrane 220, 225 may ensure that the materialof the membrane 220, 225 is not stretched under tension, which mayotherwise contribute to inaccuracies in how pressure is transferredbetween the flow conduit 251 and the chamber 252, 253. In certainembodiments, and as shown, the diaphragm membrane 220, 225 includes acircular or ring-like pattern 223, 226 which allows for the membrane 225to easily deflect and transfer pressure, which reduces the possibilityof inaccuracies arising associated with stretching, twisting,deformation or other mechanical hindrance. Any suitable patternedstructure 223, 226 may be employed. For example, as shown in FIG. 25,the patterned structure 223 may be hexagonal or polygonal in nature. Or,as shown in FIG. 26, the patterned structure 226 may involve a series ofconcentrically undulating waves. It can be appreciated that otherpatterned structures that allow for the diaphragm membrane 220, 225 tofreely flex back and forth may be possible.

The diaphragm membrane(s) 220, 225 may include any suitable material.For example, the diaphragm membrane(s) 220, 225 may include anelastomer, tegaderm, rubber, silicone, polymer, or other thin elasticimpermeable material able to form a seal between the chamber and theregion of the lumen where gas flows.

FIG. 27 illustrates an exploded view of another embodiment of the flowsensor system 250 where the diaphragm membranes 220 are each locatedbetween the flow conduit 251 and a housing portion 257 of chambers 252,253 in which respective pressure sensors 254, 255 are each enclosed. Inthis example, the diaphragm membrane 220 and the housing portion 257 ofeach chamber 252, 253 is structured so as to come into mutual alignmentand provide an impermeable seal between the flow conduit 251 and therespective chamber 252, 253, allowing for the pressure within a lumendefined by the flow conduit 251 within the immediate vicinity of thediaphragm membrane 220 to be more accurately determined. As discussedabove, the diaphragm membrane(s) 220 and associated pressure sensor(s)254, 255 (e.g., chamber 252, 253 in which a pressure sensor 254, 255 ishoused and sealed by a diaphragm membrane 220) may be provided as partof either the disposable portion or the reusable portion of the flowsensor system 250. For example, the housing portion(s) 257 and diaphragmmembrane(s) 220 shown in FIG. 27 may be integrated into the reusableconnector component 258, which may be connected to the flow conduit 251;or, the housing portion(s) 257 and diaphragm membrane(s) 220 may beintegrated into the disposable flow conduit portion 259, to which areusable connector component 258 may be connected.

FIGS. 28-29 and 30-31 show embodiments of an assembly of a reusableconnector portion 258 and a disposable flow conduit portion 259. Thereusable connector portion 258 includes a circuit board 260 (includingpressure sensors 254, 255), chamber housings 257 (substantiallysurrounding respective pressure sensors 254, 255) and diaphragmmembranes 220, 225 disposed at respective ends of the chamber housings252, 253. Here, as shown in FIGS. 28 and 30, the circuit board 260,chamber housings 257 and diaphragm membranes 220, 225 are all part ofthe reusable portion 258 of the flow sensor system 250. The reusableportion 258 may include diaphragm membranes 220, 225 so that thepressure sensors 254, 255 (which are now reusable rather thansingle-use) may be adequately protected within the chamber 252, 253. Thedisposable flow conduit portion 259 includes several components similarto those described above with respect to other embodiments (e.g., flowrestrictor 256, flow conduit 251, etc.), and further includes chamberhousings 257 and diaphragm membranes 220, 225 that have complementaryfeatures corresponding to their reusable counterparts. That is, uponconnection of the reusable 258 and disposable portions 259, the chamberhousings 257 and diaphragm membranes 220, 225 of the reusable connectorportion 258 may suitably engage with the corresponding chamber housings252, 253 and diaphragm membranes 220, 225 of the disposable connectorportion 259, to allow for pressure equalization between the lumen 261 ofthe flow conduit 251 and the space within chamber 252, 253 where thepressure sensor 254, 255 is present.

As shown in FIGS. 29 and 31, when the reusable and disposable portions258, 259 are connected, the respective chamber housings 257 maystructurally engage so as to provide for appropriately sized chambers252, 253 within which corresponding pressure sensors 254, 255 mayreside. In some embodiments, the respective chamber housings 257 mayengage to form a firm connection between the reusable and disposableportions 258, 259. For example, while not expressly shown in thefigures, the complementary features of respective chamber housings 257may engage via interlocking members, a friction fit, a tapered contactconnection, a bayonet connection, etc. Further, as noted above, thecorresponding diaphragm membranes 220, 225 may also engage in a mannerthat allows for accurate pressure equalization between the flow conduit251 and chamber space. For example, the corresponding diaphragmmembranes 220, 225 may have complementary patterned structures 223, 226that are able to fit snugly together.

In FIGS. 28 and 29, the diaphragm membranes 220 have a hexagonal pattern223, similar to that shown in FIG. 25. Similarly, in FIGS. 30 and 31,the diaphragm membranes 225 have a concentric wave pattern 226, similarto that shown in FIG. 26. In both cases, the diaphragm membranes 220,225 of the reusable connector portion 258 complement the diaphragmmembers 220, 225 of the disposable flow conduit portion 259, such thatupon connection of the reusable and disposable parts 258, 259, as shownin FIGS. 29 and 31, pressure equalization across the diaphragm structure220, 225 is still able to occur, resulting in accurate pressurereadings.

When subject to varying pressures (e.g., due to changing altitude),because the diaphragm membrane 220, 225 is sealed to the chamber 252,253 in which the pressure sensor 254, 255 is located, the diaphragmmembrane 220, 225 may have a tendency to bulge inward or outward, whichmay affect pressure readings. For example, at high altitude, thesurrounding pressure may be lower than atmospheric, providing lessambient resistance to the diaphragm membrane 220, 225 as compared toatmospheric pressure. Similarly, at surrounding pressures higher thanatmospheric, the ambient resistance to the diaphragm membrane 220, 225may be greater than atmospheric pressure.

Accordingly, it may be preferable to compensate for such fluctuation inambient pressures. In some embodiments, a rolling diaphragmconfiguration may be incorporated, such as that shown FIGS. 32-36, whichdepict a flow sensor system 300, according to an embodiment of thepresent disclosure, which includes a rolling diaphragm 350. As shown inFIGS. 34 and 35, the flow sensor system 300 includes a flow conduit 301,which defines a lumen 302 in which a flow restrictor 303 is disposed, asdiscussed above with reference to the other embodiments. Chamberhousings 304 are disposed above the flow conduit 301. The chamberhousings 304 define chambers 305, 306, in which are disposed first andsecond pressure sensors 307, 308, respectively. The pressure sensors307, 308 are connected to a circuit board 309. The flow conduit 301 andflow restrictor 303 may form part of a disposable flow conduit portion310 while the circuit board 309 and pressure sensors 307, 308 may formpart of a reusable connector portion 311, similarly to the flow sensorsystem 250 discussed above with reference to FIGS. 25-31. The chamberhousings 304 and rolling diaphragms 350 may be included in thedisposable flow conduit portion 310 or the reusable connector portion311, as also discussed above, though it is to be appreciated that if thechamber housings 304 form part of the reusable connector portion 311,then two rolling diaphragms 350 for each respective chamber 305, 306 andpressure sensor 307, 308 may be provided.

FIG. 36 provides cross-sectional representation of one of the chamber305, 306, including a housing 304, pressure sensor 307, 308 and rollingdiaphragm 350. As shown, the rolling diaphragm includes a rollingportion 351, a diaphragm membrane 352 incorporating a wavy patternedstructure 353, as discussed above, and a peripheral flange 354. Here,the diaphragm membrane 352 may move up and down relative to the chamber305, 306 to provide equilibrium between the pressure within the chamber305, 306 and the surrounding ambient pressure. Once the rollingdiaphragm 350 equilibrates, the diaphragm membrane 352 is able toaccurately transfer pressure between the flow lumen 302 and the chamber305, 306. The rolling portion 351 deflects or is manipulated accordingto the ambient pressure (atmospheric pressure) to allow the diaphragmmembrane 351 to move up and down relative to the chamber 305, 306. Theperipheral flange 354 allows for the rolling diaphragm 350 to be securedbetween the chamber housing 304 and the flow conduit 301.

For example, FIGS. 33, 35, and 36 (solid diaphragm) show the rollingdiaphragm 350 having equilibrated with ambient pressure (atmosphericpressure) at relatively low altitude. Here, there is a sufficientdistance D1 (shown in FIG. 36) between the rolling portion 351 of therolling diaphragm 350 and the circuit board 309 so that an accuratepressure reading can be obtained. And as such, the wavy patternedstructure 353 of the diaphragm membrane 352 is able to move freely backand forth to suitably transfer pressure between the flow lumen 302 andthe chamber 305, 306.

In FIGS. 32, 34, and 36 (dashed diaphragm), the chamber 305, 306 isexposed to higher altitude (lower than atmospheric pressure), and soinstead of the diaphragm membrane 352 bulging outward, the rollingdiaphragm 350 moves down with respect to the chamber 305, 306 untilmechanical equilibrium is reached between the pressure within thechamber 305, 306 and the surrounding ambient pressure (lower thanatmospheric pressure). Accordingly, the distance D2 between the rollingportion 351 of the rolling diaphragm 350 and the circuit board 309 (whenthe chamber 305, 306 is subject to lower than atmospheric pressure) iscomparatively greater than the distance D1 (when the chamber is subjectto atmospheric pressure). The wavy patterned structure 353 of thediaphragm membrane 352 is thus able to move back and forth unfettered,so as to be able to transfer pressure between the flow lumen 302 and thechamber 305, 306, to obtain substantially accurate readings.

Returning to FIGS. 7 and 10-13, the flow sensor system 100 comprises twomembranes 108 disposed between the lumen 102 and a respective one of thetwo chambers 114, 123. More specifically, each membrane 108 ispositioned on the interior surface of the flow conduit 101 over therespective conical/tapered cavity 120 leading to the respective opening119 and chamber 114, 123. Each membrane 108 comprises a thin, bendablefilter layer 126 that comprises a breathable, hydrophobic material thatis configured to allow for the passage of gas through the membrane 108and also act as a barrier to obstruct or prevent the passage of moistureand debris through the membrane 108. The conical/tapered cavity 120 isalso shaped to allow for the surface area of the bendable filter layer126 to be enlarged to a sufficiently large surface area so as tominimize or otherwise reduce the impedance to the flow gas to thesensors 131, 132 created by the bendable filter layer 126. According toone particular embodiment of the present disclosure, each bendablefilter layer 126 has an approximate surface area of betweenapproximately 10 mm² and 100 mm², or approximately 30 mm² and 60 mm², or45.6 mm² or any other appropriate surface area.

According to one embodiment of the present disclosure, the filter layer126 may comprise at least one of the following materials:polytetrafluoroethylene (PTFE), of the type sold under the brand nameTEFLON®; expanded polytetrafluoroethylene (ePTFE), of the type soldunder the brand name GORE-TEX®; and woven fabric. In some embodiments,the filter layer includes an oleophobic and/or hydrophobic material. Thefilter layer 126 may have pores between 0.1 and 1 micron (e.g.,approximately 0.5 μm) with polyester/polyethylene scrim. Alternatively,the filter layer 126 may be coated with a breathable hydrophobicmaterial that comprises one of the following materials:polytetrafluoroethylene (PTFE) and expanded polytetrafluoroethylene(ePTFE). The filter layer 126 of each membrane 108 is configured toallow gas to pass through from the lumen 102 to the respective opening119 and chamber 114, 123 in which the respective one of the first andsecond absolute pressure sensors 131, 132 is positioned to obstruct orprevent the passage of liquid and debris, such as dust, sputum, orsaliva, from passing through to interfere with the operation or readingsof the first and second absolute pressure sensors 131, 132.Alternatively, a single membrane 108 may be provided that extends acrossboth cavities 120 and openings 119 or more than two membranes 108 may beprovided.

As shown in FIGS. 11-13, in addition to the filter layer 126 eachmembrane 108 may optionally include an adhesive layer 127 surroundingthe filter layer 126 for applying the membrane 108 to the interiorsurface of the flow conduit 101 and a flap 128 for securing the membraneon the respective first and second piece 106, 107 of the flow conduit101. The flap 128 comprises holes 129 defined therein that may receivepins 118 extending from the end of the respective first and second piece106, 107 of the flow conduit 101 where the piece 106, 107 is attached,formed or otherwise secured to the other piece 106, 107. Each piece 106,107 may optionally include ribs 117 provided therein on the interiorsurface that hold the respective membrane 108 in place. In someembodiments, the membrane(s) 108 are held in place by a structure and/oradhesive other than the depicted supporting ribs 117. During assembly,each membrane 108 is applied to the interior surface of a respectivepiece 106, 107 of the flow conduit 101 and against the ribs 117 in therespective piece 106, 107 such that the flap 128 is flexed to extendover the ends of the ribs 117 with the pins 118 being received in theholes 129 defined in the flap 128. The flaps 128 are thereby securedbetween the pieces 106, 107 when the pieces 106, 107 are fastenedtogether. Though, it can be appreciated that the membrane(s) 108 may becoupled to the flow conduit by any other suitable method. For instance,the membrane(s) 108 and a corresponding receiving region of the flowconduit 101 may have complementary structural features which allow forthe membrane(s) 108 to be coupled thereto. As an example, edges of themembrane(s) 108 may be able to slide into complementary slots/recessesof the flow conduit 101, for holding the membrane(s) 108 in place.

Certain regions of the flow sensor system may be sensitive to theaccumulation of water and/or debris, for example, associated withinspiratory and expiratory flow. For example, if water or debriscollects at the flow restrictor, or portions thereof, the(pre-calibrated) pressure-flow relationship may be affected. Similarly,if water or debris collects at or around the membrane (e.g., porousbarrier membrane, non-porous diaphragm barrier membrane, or othermembrane-type component) between the lumen of gas flow and the chamberwithin which the pressure sensor(s) are located, the accuracy ofpressure sensing may also be affected. Accordingly, it may be preferablefor water and/or debris to be diverted from the more sensitive regionsof the flow sensor (e.g., regions that may contribute to the overallaccuracy of flow determination) to other neighboring regions that areless sensitive to determining the accuracy of flow. Hence, one or moresensitive regions of the flow sensor (e.g., membrane between lumen offlow conduit and pressure sensor, flow restrictor) may exhibit a greaterlevel of hydrophobicity than the neighboring region(s) adjacent to thesensitive region(s). For instance, the flow sensor may be configuredsuch that water is less likely to condense at the sensitive region(s)but more likely to condense or otherwise collect at region(s) thatneighbor the sensitive region(s).

Referring to FIGS. 13(a) and 13(b), the membrane 108 may include amaterial (e.g., polytetrafluoroethylene) that exhibits a greater levelof hydrophobicity than regions neighboring the membrane, such as thesurface of the flow conduit immediately adjacent to the membrane. Themore hydrophobic material may comprise the membrane, or may be coatedthereon. The surface of the flow conduit neighboring the membrane mayinclude a plastic or polymeric material that is less hydrophobic (ormore hydrophilic) as compared to the membrane, resulting in wateraccumulation or diversion away from the membrane and toward theneighboring region. Or, the membrane itself may have regions whichexhibit different levels of hydrophobicity. For example, the filterlayer 126 may include a relatively hydrophobic material (e.g.,polytetrafluoroethylene), and the surrounding adhesive layer 127 may behydrophilic, or less hydrophobic, in comparison to the filter layer 126.Due to such a structure, water may tend to accumulate or be divertedaway from the filter layer 126 and toward the neighboring adhesive layer127, or even further away.

Or, referring to FIGS. 13(c) and 13(d), in some cases, other portions ofthe flow sensor may be sensitive to overall accuracy of the flowdetermination. For instance, the internal structure of the flow conduitmay be shaped so that the flow through the lumen is substantiallylaminar. In general, such smooth flow may lead to predictable, accuratepressure/flow readings. FIG. 13(c) illustrates an example where gas flowF through the conduit is generally unimpeded. However, the accumulationof water and/or debris in certain areas of the flow conduit may affectthe pressure/flow readings. For example, the buildup of water and/ordebris in such areas may give rise to undesirably turbulent flow,resulting in less accurate measurements. FIG. 13(d) depicts an instancewhere water and/or debris is collected at a sensitive region S, in amanner where gas flow in proximity to the accumulation is affected.

Accordingly, it may be desirable for certain regions of the flow conduitto be more resistant to such accumulation than others. Similar to thatof other sensitive regions of the flow sensor system, certain regions ofthe flow conduit may include a material (e.g., polytetrafluoroethylene)that exhibits a greater level of hydrophobicity than regions neighboringthe more sensitive regions. The sensitive region(s) of the conduit maybe made up of the more hydrophobic material, or the more hydrophobic maybe coated thereon. Alternatively, neighboring regions around thesensitive region may include a material that is comparatively morehydrophilic than the sensitive region. For example, the surface of theflow conduit neighboring the more sensitive region(s) may include aplastic or polymeric material that is less hydrophobic (or morehydrophilic) as compared to the surface of the sensitive region(s),resulting in water accumulation or diversion away from the sensitiveregion(s) and toward the neighboring region(s).

Additionally, the flow conduit 101 may also incorporate a rim made froma hydrophilic material (not shown), or a material that is comparativelyless hydrophobic than more sensitive regions of the flow sensor, forinstance in one of the connection portions 116, 124, that is configuredto collect moisture and debris from the gas flowing through the lumen102. The flow conduit 101 may also comprise a condensation element (notshown), such as a gridded aluminum plate, that is configured to collectmoisture and debris from the gas flowing through the lumen 102. Such aconfiguration may help to mitigate the accumulation or presence ofcontaminants that would otherwise contribute to inaccuracies in the flowsensing measurements.

The circuit board may be secured to the flow conduit by any suitablemanner, for example, via mechanical attachment (e.g., welding, adhesive,interference fit, complementary coupling features, etc.). With referenceto FIGS. 11 and 12, a ring hole 115 may be provided in the top surfaceof each of the first and second pieces 106, 107 around the respectivechamber 114, 123. A sealant or adhesive may be placed within the ringholes 115 to secure the circuit board 110 to the upper surface of theflow conduit 101. The upper surfaces of the first and second pieces 106,107 also comprise upwardly extending pins 121. The pins 121 are receivedin pin holes 130, shown in FIG. 13, extending through the circuit board110 to assist in positioning and securing the circuit board 110 on theupper surface of the flow conduit 101.

With reference to FIGS. 6-9, 14, 15, and 18, an adapter 112 may bedisposed on an upper surface of the circuit board 110 and iselectronically connected to the circuit board 110. In this embodiment,the trace contacts of the circuit board to which the adapter 112provides electrical communication with the connector 113 extend along adirection substantially parallel to the long axis of the circuit board,although other configurations may be possible. The adapter 112 isprovided to establish electronic communication between the circuit board110 and a connector 113, as will be discussed in further detail below.As shown in FIG. 14, the circuit board 110 may also incorporate at leastone heating element 133, such as a resistive device (e.g., electricalresistor), that is configured to be energized to generate a small amountof heat upon the application of a current in or near the chambers 114,123 defined in the upper surface of the flow conduit 101. The heatgenerated by the heating element(s) may be sufficient to prevent orotherwise limit the risk of fluid accumulation near the first and secondabsolute pressure sensors 131, 132. That is, while the membrane(s) 108may act as a barrier to keep liquid water in the lumen from enteringrespective chambers 114, 123, the membrane(s) may allow water vapor topass there through. In this example, the heating element(s) may raisethe local temperature around the surface of the pressure sensor(s) in amanner suitable to prevent or otherwise mitigate against the risk ofcondensation of water vapor that may be present at the pressuresensor(s). In some cases, a single heating element may be used toprevent condensation of the pressure sensors, or multiple heatingelements may be used, for example, dedicated heating elements for eachpressure sensor (e.g., heating elements located adjacent to eachpressure sensor).

FIGS. 14(c)-14(d) depict another embodiment of a circuit board 110Awherein multiple heating elements are employed. FIG. 14(c) shows anupper perspective view of the circuit board 110A having two heatingelements 1001 located on either side of the trace contacts 1002. Here,in contrast to the configuration provided above with respect to the FIG.14, the trace contacts 1002 of the circuit board 110A, to which theadapter 112 provides electrical communication with the connector 113,extend laterally in a direction substantially perpendicular to the longaxis of the circuit board 110A. Such a configuration may be preferableso that the heating elements 1001 (e.g., resistors) may be suitablyplaced in close proximity to the pressure sensors 131, 132. FIG. 14(d)shows a lower perspective view of the circuit board 110A, which showsthe two pressure sensors 131, 132 in close proximity to respectiveheating elements 1001, which are located on the other side of the board110A.

As shown in FIGS. 6-9, 15, and 18, the flow sensor system 100 alsocomprises a cover 111 for the circuit board 110. The cover 111 ispositioned on the upper surface of the flow conduit 101 over the circuitboard 110. Both the circuit board 110 and the cover 111 are shaped tocorrespond to the shape of the upper surface of the flow conduit 101 inorder to fit on the flow conduit 101 and hold the circuit board 110 inplace. The cover 111 comprises an opening and holder 134 for the adapter112 on the circuit board 110 so that the adapter 112 may extend throughthe cover 111 and be supported in a position where it can establishelectronic communication with the connector 113. The cover 111 alsocomprises an alignment disk 135 positioned on the top of the cover 111.The alignment disk 135 is configured to provide a guide for positioningthe connector 113 so that the connector 113 may be electronicallyconnected to the adapter 112 and to limit lateral movement of theconnector 113 once the connector 113 is connected to the flow conduit101. The alignment disk 135 may be recessed from the bottom forcomponents of the circuit board 110, such as resistors and/or otherelectrical components. The cover 111 may also incorporate internalchambers 137 to accommodate components on the circuit board 110 and/orother features of the flow sensor system. The cover 111 comprises aplurality of pin holes 136 extending through the cover 111. The pinholes 136 are configured to receive the pins 121 extending from theupper surface of the flow conduit 101 in order to assist in positioningand securing the cover 111 on the upper surface of the flow conduit 101.

FIGS. 15(c) and 15(d) illustrate another embodiment of a cover 111A forthe circuit board 110A that complements the configuration shown in FIGS.14(c) and 14(d). FIG. 15(c) shows an upper perspective view of the cover111A, showing an alignment disk 1003 configured to mechanically assistpositioning of the connector 113, for establishing a suitable electricalconnection. FIG. 15(d) shows a lower perspective view of the cover 111Athat includes a recess 1004 to provide space for components of thecircuit board 110A, such as resistors and/or other electricalcomponents.

FIG. 15(e) depicts an implementation where the adapter 112 is held inplace by the cover 111. In this case, the cover 111 includes barbs 111 bthat protrude toward the adapter 112 and are tapered so as to facilitateplacement of the adapter 112 on the circuit board 110, and to hold theadapter 112 securely against the circuit board 110 when placed.Accordingly, in this instance, the adapter 112 remains in firmelectrical connection with the circuit board 110 without requiringfurther assistance (e.g., from an adhesive) to ensure that theelectrical connection is maintained.

With reference to FIGS. 6, 7, and 16-18, the flow sensor system 100 alsocomprises the connector 113 that places the first and second absolutepressure sensors 131, 132 in electronic communication with a processor145. The processor 145 may be configured receive the absolute pressuremeasurements from the first and second absolute pressure sensors 131,132 and may determine at least one of a flow rate and a volume of gasflowing through the lumen 102 of the flow conduit 101 based on thepressure measurements in the first and second regions 103, 104 of theflow conduit 101. The processor 145 may also be configured to generate asignal outputting the determined flow rate and/or volume of gas flowingthrough the flow conduit 101 and/or to send a feedback signal to adjustthe gas flow through the lumen 102 of the flow conduit 101 based on atleast one of the determined flow rate and the volume of gas flowingthrough the lumen 102.

Though, it is not required for the processor 145 to perform each of theaforementioned calculations. For example, in some embodiments, theprocessor 145 may perform none of these calculations and simplystore/transmit signals arising from the pressure sensors to anothercomputing device for further analysis and processing. Or, the processor145 may perform some of these calculations, such as determining the flowrate through the conduit based on the signals sent from the pressuresensor (based on a pre-calibrated pressure look up table) and mayfurther perform a mathematical integration resulting in the flow volume.An external device (e.g., tablet, defibrillator, medical computer, etc.)may then receive those values of rate and volume and send feedbacksignals to the processor 145, which may be further output in anintuitive manner for guiding or otherwise encouraging a user to maintainand/or improve the overall quality of resuscitation.

It can be appreciated that each of the processes for analyzing themeasurement signals produced by the pressure sensor(s) 131, 132,outputting a calculated value (e.g., flow rate, flow volume, PIP, etc.),and providing a feedback signal to adjust the manner in which gas flowis provided based on the analysis of the pressure measurement signalsmay be performed at any suitable part(s) and location(s) of the overallmedical system. For example, each of these steps may be performed at thesame location by the same processor, such as a processor 145 located inthe cable head or connector 113, as discussed above. Alternatively, eachof these steps may be performed at different locations of the medicalsystem by different processors (e.g., located in the cable headconnector, another part of the flow sensor, a more distantly locatedmedical device system such as a defibrillator, monitor, tablet,computer, ventilator, etc.). For instance, the processor 145 located inthe cable head connector may analyze pressure measurement signals anddetermine the flow rate and/or volume of flow within the lumen 102 ofthe flow sensor system 100. As noted above, this same processor 145, oranother processor (e.g., located in a monitor, defibrillator,ventilator, amongst other suitable processing systems), may furtheroutput a feedback signal to adjust flow parameters (e.g., ventilationbagging, automated ventilation characteristics).

According to various embodiments of the present disclosure, at least onethe first and second absolute pressure sensors 131, 132 may beconfigured to measure the absolute pressure in immediate proximity tothe pressure sensors, a temperature of gas flowing through the lumen 102of the flow conduit 101, a humidity of gas flowing through the lumen102, and/or to measure the ambient atmospheric pressure outside of theflow sensor system 100. Alternatively, the flow sensor system 100 mayincorporate sensors that are configured to measure at least one of thefollowing other than the absolute pressure, for example, a temperatureof gas flowing through the lumen 102 of the flow conduit 101, a humidityof the gas flowing through the flow conduit 101, and an ambientatmospheric pressure outside of the flow sensor system 100. In someembodiments, the pressure sensor(s) used to determine the local absolutepressure(s) may also be used to measure the local temperature, humidity,altitude, amongst other parameters. In some cases, the pressuresensor(s) and/or one or more additional sensors may be used to sense therelative concentration of gas flowing through the conduit (e.g., oxygen,carbon dioxide concentration).

Exemplary CO2 concentration sensors may include those provided incapnographs that measure infrared light absorption. Oxygen gas partialpressure may be measured by a suitable ppO2 meter such as those used inSCUBA-diving, or re-breathing apparatus. A specific example is thePSR-11-33-NMI oxygen sensor manufactured by Analytic Industries, Inc.(Pomona Calif.). This sensor works off the principle of anelectro-galvanic fuel cell. Oxygen concentration sensing may also bedone with an oxygen optode. In general, an oxygen optode is a sensorbased on optical measurement of the oxygen concentration. In someexamples of oxygen optodes, a chemical film is glued to the tip of anoptical cable and the fluorescence properties of this film depend on theoxygen concentration. Fluorescence is at a maximum when there is nooxygen present. When an O2 molecule is present and collides with thefilm, this quenches the photoluminescence. For a given oxygenconcentration there will be a specific number of O2 molecules collidingwith the film at any given time, and the fluorescence properties will bestable. Thus, by observing the fluorescence properties O2 concentrationcan be determined.

As provided herein, the total volume of ventilation gas delivered to andfrom the lungs may be calculated by measuring the continuous flow ratefor each individual inhalation and exhalation and then integrating theflow over time to compute volume. As concentrations may be available foreach of the measured gases for each instant, the volumes delivered foreach ventilation for each of the specific gases may also be calculatedalong with the volume delivered for all other gases not measured. In oneembodiment, the measured gases are CO2 and oxygen, with the remaininggases being predominantly nitrogen. In other embodiments, gasconcentrations for other gases may be provided such as additive gasesthat have therapeutic value such as anaesthetic gases, nitric oxide or anoble gas such as Argon.

As discussed further below, the minute-volume, as understood by thoseskilled in the art, for each of the measured constituent gases can becalculated. In general, minute-volume is the quantity of gas deliveredto the patient, or exhaled from the patient in the case of CO2, over aone-minute period. Unlike tidal volume which is the volume delivered fora particular breath, minute volume is based on the one-minute period.The calculated minute-volume for any point in time may be calculated bysumming each of the individual tidal volumes in the previous minute, orit may be estimated based on the tidal volumes of breaths occurringwithin some predefined time period in the immediate past.

The processor 145, or one or more processors positioned elsewhere fromthe connector (e.g., located at the flow sensor conduit and/or at amedical device to which the flow sensor is connected), is configured tocompensate for effects of altitude, humidity of the gas flowing throughthe lumen 102 and/or temperature of the gas flowing through lumen 102 indetermining the at least one of the flow rate and the volume of gasflowing through the lumen 102.

FIG. 22 illustrates the relationship between the flow of gas, thetemperature of gas and time in the flow sensor conduit for aspontaneously breathing person. The solid line illustrates flow inliters/minute and the dashed line illustrates temperature in degreesCelsius. For a particular flow sensor orientation, FIG. 22(a) measuresinspiratory flow to the patient as negative (below the 0 point of thehorizontal axis) and expiratory flow from the patient as positive (abovethe 0 point of the horizontal axis). Here, the flow rate and temperatureappear to be substantially out of phase. When the flow sensor is flippedaround so as to be oriented in a reverse orientation, FIG. 22(b)measures inspiratory flow to the patient as positive and expiratory flowfrom the patient as negative. In this case, the flow rate andtemperature appear to be substantially in phase. As can be appreciatedfrom FIG. 22, the temperature of the gas within the flow sensor conduitrises in response to warm gas being exhaled by the patient into the flowsensor and correspondingly drops as cooler gas (e.g., gas at roomtemperature, typically lower in temperature than expired air) is inhaledby the patient. In particular, during expiration, the temperatureincreases and reaches a peak shortly after the end of expiration; andconversely, during inspiration, the temperature decreases and reaches aminimum shortly after the end of inspiration. Accordingly, by measuringthe temperature of the gas within the flow conduit 101 in conjunctionwith the absolute pressures within the first and second regions 103,104, it is demonstrated that the temperature may be used as an indicatorfor the direction of flow (inspiratory or expiratory) that is occurringthrough the flow sensor.

Based on the above discussion, the processor 145 and/or a user candetermine the direction of flow through the lumen 102 based on thetemperature measurement from the sensor(s) of the flow sensor systemwhether flows are expiratory, due to the patient exhaling gas throughthe flow conduit 101, or inspiratory, due to gas being delivered to thepatient through the flow conduit. This may further allow the processor145 and/or a user to determine how the flow sensor system 100 isoriented within the ventilation assembly and which of the sensors 131,132 is oriented toward the patient and which is oriented away from thepatient and provide an operator an indication of the orientation of theflow sensor system 100. The processor 145 can also use thesemeasurements to determine inhalation and exhalation volumes separatelybased on the determination of whether flows are inspiratory orexpiratory. Accordingly, the processor 145, or one or more processorspositioned elsewhere from the connector (e.g., at the flow sensorconduit and/or at a medical), is configured to determine at least one ofthe flow rate, the direction of flow and volume of gas flowing throughthe lumen 102 based on the pressure measurements and at least one of thefollowing: the temperature measurement, the humidity measurement, andthe ambient atmospheric pressure.

As discussed herein, the flow sensor system may be able to determineboth the flow rate/volume through the conduit and the direction of flow.That is, both the inspiratory and expiratory flow rate/volume may bedetermined. Accordingly, the system may further be able to detect thepresence of a leak. For example, if there is no leak, the inspiratoryand expiratory volumes will be substantially the same. Conversely, if aleak exists, the inspiratory and expiratory volumes will noticeablydiffer. In certain embodiments, if the difference in magnitude betweeninspiratory flow volume and expiratory flow volume is high enough tomeet a predetermined threshold, then the system may indicate that apossible leak exists. When it is determined that a leak is present, thesystem may produce a signal to alert the user, for example, to checkthat the ventilation connection(s) are appropriately sealed.

For instances where the patient may be experiencing respiratorydistress, and is not in cardiac arrest, the patient may be fitted with anon-rebreather mask (NRB) or sealed mask, which is used to assist in thedelivery of oxygen therapy. A patient wearing a NRB should be able tospontaneously breathe. The NRB allows for high concentrations of oxygento be delivered, and has one or more openings through which expired airis permitted to travel. Hence, if breaths are spontaneous and only asmall amount of expiratory volume is detected, the system may detectthat a NRB mask has been applied to the patient. In such cases, onlyinspiratory volumes may be accurate, as expiratory air is allowed totravel out of the mask through the opening(s). Thus, if it is determinedthat a NRB mask is being used, the flow sensor system may reportinspiratory flow data, without reporting expiratory flow data.

The flow sensor system may also be useful to help determine whether anintubation tube is correctly placed. During intubation, at times, theendotracheal (ET) tube may be mistakenly misplaced into the esophagusrather than the trachea. It is also not uncommon for the ET tube tobecome dislodged during the course of resuscitation, or as a result ofvibrations during transport by ambulance or other mode oftransportation. To confirm placement of the endotracheal tube,paramedics typically rely on EtCO2 measurements. However, when patientshave decreased perfusion as in cardiac arrest, the accuracy of EtCO2 maybe unreliable. Hence, confirming whether there flow is present withinthe airway, in combination with EtCO2 and impedance measurements, mayaid in the assessment of whether the tube is properly in place. When apositive pressure breath is delivered to a properly placed endotrachealtube, the EtCO2 and/or impedance would be expected to noticeably change.If the EtCO2 and/or impedance does not change, or is below a thresholdvalue, the tube may be considered to be misplaced.

Transthoracic impedance (TTI) may also be useful for confirmingendotracheal tube placement. Detection of a pressure waveform pulse maybe used to initiate an analysis of either an accelerometer waveform, aTTI waveform, or both to see if the attempt to deliver respiratory gasvia ventilation is delivering the gas to the lungs or to the stomach(via the esophagus). If the gas is delivered to the lungs, there will bean associated pulse waveform of the actual measured displacement of thesternal region where the accelerometer is placed (double integration ofthe accelerometer waveform will show a rising sternum). Alternatively, aTTI measurement can be used, as air delivered to the lungs will cause arise in transthoracic impedance (TTI). Due to both the compressiblenature of the gas as well as the fact that the lungs expand bothsternally and diaphragmatically, there will be some delay followinggeneration of the pressure pulse before the associated displacementwaveform is observed from the accelerometer or the TTI measurement.

In some implementations, two pulse detection methods may be used. Thefirst time aligns the pressure waveform pulse with the pulse waveform ofthe sternal displacement and TTI measurement. If the delay from theleading edge of the pressure pulse waveform to the leading edge of thedisplacement and TTI waveforms is less than 700 milliseconds, and thedelay of the trailing edge of the pressure pulse waveform to thetrailing edge of the displacement and TTI waveforms is also less than700 milliseconds, then the displacement and TTI pulse waveforms areconsidered to be as a result of the ventilation cycle. The second pulsedetection method uses the acceleration waveform to detect the firstinitial movement of the sternum due to the ventilation. The displacementwaveform is calculated, and the first pulse of the acceleration signalthat contributes to the displacement pulse determines the start of thesternal displacement pulse. A more accurate onset of motion of thesternum due to ventilation can oftentimes be achieved in this manner. Ifthe displacement and TTI waveforms are found to be the result of theventilation pressure waveform pulse, then the ET tube is considered tobe in the proper location in the trachea and not in the esophagus.

If the intubation tube is placed in the esophagus, then the expired flowsignal would be significantly less than the inspired flow volume.Though, if the intubation tube is correctly placed in the trachea, thenthe expired and inspired flows will be comparable. The shape of theinspiratory and expiratory flow waveforms would also differ depending onwhether the intubation tube is placed in the esophagus versus placementin the trachea. Accordingly, for certain embodiments, in combinationwith EtCO2 and/or impedance measurements and/or other useful indicatorsof intubation tube placement, if the difference in magnitude betweeninspiratory flow volume and expiratory flow volume is high enough tomeet a predetermined threshold, then the system may indicate that theintubation might be misplaced. In such a case, the system may produce asignal to alert (e.g., via visual, audio and/or tactile feedback) theuser to check whether the intubation tube is properly placed. The systemmay be configured to continuously monitor placement of the intubationtube.

A visual indicator may provide visual feedback to the rescuer as towhether or not the ET tube has been properly placed. When the tube isdetermined to be properly placed, the system may activate a green LED ata suitable location (e.g., on the exterior of the flow conduit, on theconnector, etc.). If the previous ventilation attempt resulted in thedetermination of an improperly placed ET tube, then the system mayactivate a red LED of the visual indicator. The visual indicator mayalso include a series of LEDs configured as a dual color bar-graph toindicate the tidal volume of each successive ventilation, with the colorof the LED bars indicative of whether or not the tube is properly placed(green indicating proper placement; red-indicating improper placement).Alternatively, separate indicating lights may be provided for airway andbreathing, to indicate proper ET tube placement and ventilation tidalvolume, respectively. Or, an audio alarm (e.g., verbal, tone) mayactivated to provide feedback to the rescuer if the ET tube is placedimproperly or becomes dislodged. In an embodiment, if an improperlyplaced ET tube is not corrected, then the alarm may escalate inintensity (e.g., increasing volume with time).

With reference to FIGS. 6-9 and 16-18, the processor 145 is incorporatedin the connector 113, which is configured to be removably coupled to theflow conduit 101 to place the first and second absolute pressure sensors131, 132 in communication with the processor 145. That is, when theconnector 113 is coupled to the flow conduit 101, electricalcommunication is established between the pressure sensors 131, 132 andthe processor 145, and other electrical components (e.g., computingdevice, defibrillator, tablet, monitor, etc.) to which the cable 146extends. The connector 113 comprises a molded outer shell or housing 138that contains the internal assembly 142 of the connector 113, comprisingthe processor 145. When the connector 113 is mounted on the flow conduit101, the housing 138 is engaged by snap arms 109 extending from theupper surface of the flow conduit 101. The housing 138 comprises anindentation 140 formed therein and each of the snap arms 109 comprises aprotuberance 147 formed along its length. The protuberances 147 on thesnap arms 109 engage within the indentation 140 on the housing 138 tomaintain the engagement between the connector 113 and the snap arms 109while allowing the connector 113 to rotate with respect to the flowconduit 101 without becoming disengaged and allowing the connector 113to be coupled to the flow conduit 101 from a variety of angularorientations. The snap arms 109 are flexible so that they may deflect asuitable amount to allow the connector 113 to be connected to andremoved from the flow conduit 101. It can be appreciated that thecomplementary snap arms and protuberances are not required aspects ofthe present disclosure, as the flow conduit and the connector may beengaged via any suitable configuration, such as via magnetic coupling,interference fit, amongst others.

In some embodiments, as shown, when connected to the flow conduit, theconnector may swivel about a transverse axis of the flow conduit,similar to that of a turret. In the configuration shown in the figures,the cable 146 extends horizontally relative to the flow conduit alongthe plane about which the connector 113 swivels. Though, in someembodiments (not shown), the cable may extend vertically relative to theflow conduit. For example, instead of swiveling about a two dimensionalplane with a circular range of motion, the connector and flow conduitengagement may be constructed such that the cable may have a generallyhemispherical or dome-like range of motion.

As shown in FIGS. 17 and 18, the internal assembly 142 of the connector113 also comprises a contact pad 141 accessible through the bottom ofthe outer housing 138. The contact pad 141 comprises a plurality ofconductive elements 143, which are arranged in concentric circles on thecontact pad 141 in a bulls-eye pattern. The contact pad 141 is incommunication with the processor 145 and the cable 146, which extendstoward another medical device system, via a plurality of signalconductors 144 also disposed within the outer housing 138 of theconnector 113. As shown in FIG. 18, the adapter 112 on the circuit board110 comprises a plurality of alternating conductive and non-conductivelayers arranged in a striped pattern (“zebra” pattern) such that theconductive layers are spaced to correspond to the radial spacing of theconcentric conductive elements 143 on the contact pad 141. Accordingly,when the connector 113 is connected to the flow conduit 101, the adapter112 can establish electronic communication with the connector 113 viacontact between the conductive layers on the adapter 112 and theconductive elements 143 on the contact pad 141. Since the conductiveelements 143 on the contact pad 141 are arranged in concentric circles,when the connector 113 is connected to the flow conduit 101, electroniccommunication may be established from all angles with respect to theflow conduit 101 within a two-dimensional plane. The connector 113 canalso be rotatably coupled to or otherwise swivel about the flow conduit101 while maintaining electrical communication between the first andsecond absolute pressure sensors 131, 132 and the processor 145. Also asshown in FIG. 18, the alignment disk 135 and the cavities 137 on thecircuit board cover 111 engage the housing 138 to align the contact pad141 on the connector 113 with the adapter 112 and maintain the connector113 in a lateral and longitudinal position on the flow conduit 101 whileallowing the connector 113 to rotate in place.

In some embodiments, the alternating conductive and non-conductivelayers of the adapter 112 are spaced in a substantially fine manner,with a higher pitch than the example described above where theconductive layers are spaced to correspond to the radial spacing of theconcentric conductive elements 143. For instance, the conductive layersmay be spaced less than 0.5 mm (e.g., approximately 0.1 mm, with 230-250conductive layers per inch) with respect to one another. That is, theconductive and non-conductive layers of the adapter 112 may be spacedsubstantially closer to one another than that of the spacing of thetraces of the circuit boards. Such a configuration may help to ensurethat matching traces on circuit boards above and below the adapter 112are vertically connected, without horizontal misconnection(s).Accordingly, tolerances in the spacing of the traces on circuit boardsabove and below the adapter may be configured such that misconnectionsbetween traces are prevented. In some cases, the non-conductive layer(s)of the adapter may exhibit a suitable level of flexibility, for example,such layers may be made of a conformable material such as rubber,silicone, plastic, amongst other material, allowing for the overalladapter to be compressible (particularly if the conductive layers arecomposed of a rigid material). It may be preferable for the adapter tobe compressible, for example, by having a relatively high pitch ofalternating conductive and non-conductive layer, so as to ensuresuitable connection between traces of the circuit boards positionedabove and below.

The connector 113 may also comprise a cable 146 extending from theprocessor 145 for placing the processor 145 in communication with amonitor and/or feedback device or to the controller for an automaticventilation system, as discussed above. The outer housing 138 of theconnector 113 comprises a strain relief housing 139 that surrounds thecable 146 as it passes through the housing 138 in order to protect theconnection between the cable 146 and the processor 145. As noted above,it is to be appreciated that the connector 113, the flow conduit 101,the circuit board cover 111, and the adapter 112 may be configured insuch a manner as to allow for the connector 113 to be connected to theflow conduit with an additional degree of freedom, i.e., in threedimensions, so that the connector 113 may also be connected from avariety of vertical angles with respect to the flow conduit 101.

In various embodiments described herein, the connector swivels orotherwise rotates about the flow conduit, although other arrangementsmay be possible. It can be appreciated that connector configurationsdescribed herein may be employed for systems other than a flow sensor.For example, such connector configurations may be used for anyappropriate medical connector systems, such as for chest compressionsensing, pulse oximetry, carbon dioxide (e.g., end tidal CO2) sensing,ECG sensing (e.g., 12-lead, 3-lead ECGs), blood pressure, amongstothers, where an electrical connection is maintained between componentsthat are permitted to rotate, pivot, turn or otherwise move relative toone another. In various embodiments, such a connector system may beapplicable for systems with disposable components. For, example, theconnector may be part of the reusable portion of the system, andconnected to the disposable part of the system. As noted above, thedisposable part of the system may include a flow conduit from which flowthere through may be determined. In other examples, the disposable partof the system may include a pulse oximeter lead, ECG lead, CPR sensorlead, etc.

It is to be appreciated that by separating the processor 145 from theflow conduit 101, the assembly of the flow conduit 101, sensors 131,132, and the circuit board 110 can be provided as a single-usedisposable unit since the assembly can be produced relativelyinexpensively. Accordingly, it is not necessary for the assemblycomponents to be sterilized after use, which can be labor intensive,jeopardize functioning of the components, and may not completely preventspread of infection or contaminants. The connector 113, on the otherhand, may be used repeatedly since the connector 113 is only exposed tothe patient or patient fluids to a limited degree in comparison to thedisposable portion of the flow sensor system, if at all. For instanceswhere the connector and/or other reusable components do come intocontact with the patient and/or fluids, etc., the exterior surface ofthe connector is easy to clean, without difficult to reach openings,such as is the case for other types of connectors, for example, USBconnectors. The connector and/or other reusable components may be madeup of materials that are resistant to harsh or corrosive treatment(s)commonly associated with cleaning products.

The connector 113 and/or other portions of the flow sensor system mayalso be configured to provide at least one of audio feedback, visualfeedback, and haptic feedback to the user to adjust the manner (e.g.,ventilation bagging, ventilator control) in which gas flow is providedthrough the lumen 102 of the flow conduit 101, based on at least one ofthe determined flow rate and volume of gas flowing through the lumen102. Accordingly, the connector 113 or another component mayadditionally incorporate a LCD screen (not shown) and/or LED light (notshown), microphone (not shown), and/or vibrator device (not shown) forproviding the feedback to the user. Alternatively, the connector 113 maybe connected to an external feedback device, such as a monitor device asdescribed above with reference to FIG. 1, via the cable 146. In certainembodiments, the flow sensor system may be in communication with adefibrillator and/or monitor for assisting a user through theresuscitative process. For example, as discussed further below, based oninformation provided from the flow sensor system, a diagnostic system(e.g., defibrillator, monitor, etc.) may display a CPR dashboardincluding a chest compression dashboard and/or ventilation dashboard, asdiscussed further below. Or, the connector, or other part of the flowsensor system, may include an LED, or other light, audio component(e.g., speaker) and/or haptic engine that provides a signal to a userfor performing various ventilation related activities. For example, thesignal may assist the user in timing ventilation bagging, providing cuessimilar to that of a metronome. Or, the signal may provide an indicationto the user to switch the type of resuscitation activity that isperformed on the patient, such as switching from applying chestcompressions to applying ventilations, or vice versa.

As discussed above, the flow sensor system 100 may include one or moreLEDs to provide feedback to a user of the flow sensor system 100. TheLED(s) may light up in a continuous and/or intermittent manner. Forexample, the LED(s) may blink or provide a series of flashes each timeventilation is to be provided to a victim, so as to provide a visualindication for a rescuer. The LED(s) may be located at any suitablelocation such that it is more likely to be seen by the rescuer, and lesslikely to be blocked visually by other ventilation components orphysical obstacles. In some embodiments, portions of the flow sensorsystem 100, such as the flow conduit 101 or other components, may bemade up of a light spreading material (e.g., dispersive polymer,translucent plastic). For example, when the light spreading material isexposed to a focused light source, the entire light spreading materialmay illuminate, making it more likely for a rescuer to notice thepattern and color of illumination of the flow sensor. Accordingly, whenthe light source turns on, it may appear to the user as if the entireflow conduit lights up.

Multiple modes of feedback may be provided (e.g., both rate and volume).For instance, a first LED may be provided as a backlight for a letter“R” for rate, and another LED may provide a backlight for a letter “V”for volume, and/or a pair of LEDs may be located on opposed sides of theletter, with lighting of an LED behind the letter indicating that therate or volume being applied by the rescuer, respectively, is correct.The LEDs to the side of the letter may be lit alternatively, dependingon whether the rescuer is being prompted to increase or decrease theirrate or volume of ventilation.

In an embodiment, a single LED light 360, such as that shown in FIG. 37,may provide feedback according to various modes. For instance, blinkingof the LED 360 may be an indication that the rescuer should ventilate.An LED 360 that is continuously lit, or blinking at a high frequency(more rapidly than if the LED 360 were blinking as a signal for therescuer to begin ventilations), may serve as a warning indication, forexample, that the patient is being over-ventilated. Such a warningindication may be triggered when the flow volume or peak inspiratorypressure has reached a preset threshold. When the LED 360 is off, nowarning signal is provided, thus, indicating that the level ofventilation provided to the patient is adequately within specifiedparameters. In some cases, a single LED 360 may emit light of differentcolors, for example, red, yellow, green, etc.

In another embodiment, as further shown in FIG. 37, multiple LED lights370 may be used. While a single LED 360 may emit multiple colors,separate multiple LED lights 370 may be configured to emit specificcolors, for example, red, yellow, green, etc. The LEDs 370 may provideindication to the user of a number of warnings and/or activities. Forexample, at the appropriate time during the resuscitation process, theLEDs 370 may signal the user to ventilate, may indicate when the flowvolume and/or peak inspiratory pressure exceeds respective thresholding.In various embodiments, a green light may indicate that the quality ofventilations are adequate and a red light may indicate that the patientis being over-ventilated. A blinking yellow light may signify that abreath should be given to the patient.

In certain embodiments, as also shown in FIG. 37, an LED ring 380 may beemployed, for example, on the top of the reusable connector 113, or atany other suitable location visible to the user. When flow volume isdetected and is within suitable parameters, the LED ring 380 may lightup according to a suitable color (e.g., green), and when the flow volumeis outside of the desired limit, the LED ring 380, or a portion thereof,may light up according to another color (e.g., yellow as a warning, redas a stronger indicator). The LED ring 380 or other LEDs may turn color,for example, from green to red, when the volume or PIP exceeds certainthresholds corresponding to when the user should be warned and when thelevels are becoming significantly more harmful to the patient. Inanother example, the LED ring 380 may blink yellow to instruct a userthat a breath should be given.

In some instances, the circumference of the LED ring 380 may provide theuser with an indication of how much volume has been and provided at anygiven time to the patient, along with a target range. As an example, atthe beginning of a breath where no volume has yet been given, the LEDring 380 may remain dim, yet as flow volume increases, the light alongthe LED ring 380 may be illuminated so as to track along thecircumference or perimeter of the device. That is, when a quarter orhalf the flow volume is reached, a quarter or half the circumference ofthe LED ring 380 may light up, respectively, for example, as a yellowcolor until the flow volume is within the target range, in which casethe LED ring 380 may light up as green. Though, when the target flowvolume is exceeded or remains outside the target range, the LED ring380, or other part of the display, may light up as red, indicating tothe user that the flow volume is outside the desired range.

As discussed above, the flow restrictor 105 is configured to interruptthe flow of gas through the lumen 102 to create the pressure drop in thelumen 102 between the first region 103 and the second region 104 fordetermining flow rate/volume. The processor 145 is configured todetermine the pressure drop based on the pressure measurements of thefirst and second absolute pressure sensors 131, 132 and to determine atleast one of the flow rate, the direction of flow, and volume of gasflowing through the lumen 102 based on the determined pressure drop. Theprocessor 145 may include a memory that incorporates a flow pressurelook up table for comparing the measured pressure drops withpre-determined flow rates and/or volumes. The processor may determinethe flow rate and/or volume of the gas flowing through the lumen 102 byreferencing the flow pressure look up table. Alternatively, theprocessor 145 may be connected to an external memory device thatcontains the flow pressure look up tables. Also as discussed above, theflow look up tables may also incorporate information accounting for theeffects of temperature and/or humidity of the gas flowing through thelumen 102 and/or the altitude/ambient atmospheric pressure on the flowrate and/or volume of the gas.

With reference to FIGS. 19(a) and 20(a)-(f), various flow restrictors150, 160, 170, 180, 190, and 200 may be used in flow sensor systemsdescribed in accordance with embodiments of the present disclosure. Eachof the flow restrictors 150, 160, 170, 180, 190, and 200 is a variableorifice flow restrictor that comprises at least one flap that deflectsunder the flow of gas through the restrictor 150, 160, 170, 180, 190,and 200 to create the pressure drop in the flow conduit 71, 101 betweenthe first and second regions. The relative pressure drop created by anyone of the flow restrictors 150, 160, 170, 180, 190, and 200 variesaccording to substantially linear and/or curvilinear profiles based uponthe flow of gas through the lumen 72, 102. As the overall constructionof the flow restrictor contributes to the behavior of the pressure-flowrelationship, it can be appreciated that the pressure-flow relationshipcan be tuned depending on the geometry of the flow restrictor. Forexample, it may be desirable for the pressure-flow relationship toexhibit linear behavior at certain flow regimes, and exhibit morecurvilinear behavior at other flow regimes. For certain embodiments, theflow restrictor may be configured to give rise to a pressure drop in theflow conduit that is non-linear (e.g., parabolic, step-linear,linear-parabolic), while allowing for high resolution measurements for awide range of flow rates (e.g., between approximately −50 L/min andapproximately 50 L/min, or outside this range, such as flow rates up to400 L/min, up to 800 L/min).

FIGS. 23 and 24 illustrate the relationship between the flow of gasthrough a lumen and the pressure drop created by a flow restrictorwithin the lumen for a variable orifice flow restrictor and a fixedorifice flow restrictor. As shown, the pressure drop created by a fixedorifice flow restrictor, such as in the flow sensor systems 20, 40discussed above with reference to FIGS. 2 and 3, varies quadraticallywith respect to the flow rate of the gas through the lumen. As such, thepressure drop created by a fixed orifice flow restrictor is relativelysmall at lower flow rates and is relatively large at higher flow rates.For example, as shown in FIGS. 23 and 24, the pressure drop created byan exemplary fixed orifice flow restrictor is approximately 10 Pa at aflow rate near 15 l/min, is approximately 40 Pa at a flow rate near 30l/min, and is approximately 1000 Pa at a flow rate of 150 l/min. Thisraises potential issues with respect to measuring the pressure dropbetween the two regions of the lumen to accurately determine the flowrate and/or volume of the gas flowing through the lumen. The pressuredrop at lower flow rates is very small, because of that the absolutepressure sensors may not be accurate enough to adequately measure thepressure drop because the pressure drop falls within the range ofresolution detectable by the sensors. Additionally, the pressure dropcreated by the fixed flow restrictor at higher flow rates becomesincreasingly large, which may result in too large of an obstruction tothe flow through the lumen and inadequate delivery of gas at the desiredflow rate and/or volume.

On the other hand, the variable orifice flow restrictor of the type usedin the flow sensor systems 60, 70, 100 discussed above with reference toFIGS. 4-18 is configured so that a relationship between the flow rate ofgas through the lumen and the pressure drop created by the restrictor islinear or substantially linear. This is because as flow rates move from−150 to +150 L/min the flap or flaps of the variable orifice flowrestrictor deflect in order to change the size of the opening.Accordingly, by configuring the opening and the geometry of the flap(s)of the variable orifice flow restrictor, the pressure drop created byvariable orifice flow restrictor can be controlled. In particular, thepressure drop created by the variable orifice flow restrictor canincreased to be relatively large compared to the flow. Morespecifically, the pressure drop at lower flow rates is large enough tobe adequately measured by the absolute pressure sensors, which leads togreater accuracy in determining the flow rate and/or volume of gasflowing through the lumen. For example, as shown in FIG. 24, thepressure drop created by an exemplary variable orifice flow restrictoris approximately 50 Pa at a flow rate near 15 l/min and is approximately125 Pa at a flow rate near 30 l/min.

At higher flow rates, the pressure drop created by the variable orificeflow restrictor is relatively small so that the flow restrictor does notcreate too large an obstruction to the flow. For example, as shown inFIG. 23, the pressure drop created by an exemplary variable orifice flowrestrictor is approximately 600 Pa at a flow rate near 150 l/min.

According to one embodiment of the present disclosure, the variableorifice flow restrictor is configured so that the relationship betweenthe pressure drop created by the flow restrictor and the flow rate ofgas flowing through the lumen extends substantially linearly along aresistance limit for the flow sensor system, as shown in FIG. 23(a). Theresistance limit is the maximum rate of pressure drop that can becreated in the flow conduit without detrimentally obstructing flow. Theresistance limit of the flow conduits 21, 41, 61, 71, 101 describedabove is 4.08 Pa/l/min for flow rates between 0-50 l/min. In otherwords, the variable orifice flow restrictor is configured to provide themaximum pressure drop at any given flow rate between −150 to +150 L/minwithout detrimentally obstructing flow. It is to be appreciated that thegeometry of the flap(s) and opening of the variable orifice flowrestrictor may be altered to provide different relationships between thepressure drop created by the flow restrictor and the flow rate of gas.The relationship created by the variable orifice flow restrictor doesnot necessarily need to be linear. Other statistical relationships arepossible to achieve the desired result of increasing the pressure dropto a detectable level at low flow rates while not going above theresistance limit for the flow conduit. The overall configuration of thevariable orifice flow restrictor is intended to optimize the pressureversus flow relationship for a given flow conduit. Ideally, the specificconfiguration of the flow restrictor will result in a pressure versusflow relationship that achieves a desired statistical relationship(linearity, steepness, smoothness, symmetry between positive andnegative pressures and is repeatable over multiple uses and multipleflow restrictors so that the behavior of the flow restrictor ispredictable.

With reference to FIGS. 19(a) and 20(a), the flow restrictor 150according to one embodiment of the present disclosure comprises a bodyconfigured to be disposed in the lumen 72, 102 of a flow conduit 71,101. The body comprises an outer portion 151 that surrounds an opening152 and a flap 153 disposed in the opening 152. The outer portion 151may provide mechanical reinforcement so that the flow restrictor 150 isfirmly secured within the lumen of the flow conduit in a substantiallyvertical position relative to the horizontal direction of fluid flow. Asshown, a single flap is provided in the opening, although for certainembodiments, the flow restrictor may include multiple flaps (e.g., flapwith slits, and/or flaps having varying orientation(s) around a commoncentral region as described further below). The flap 153 is coupled tothe outer portion 151 at a side of the opening 152. As discussed above,the flap 153 is configured to deflect from the opening 152 due to gasflow through the flow restrictor 150. The amount of deflection of theflap 153 is variable based upon the flow of gas through the lumen 72,102 to create a substantially linearly variable pressure drop and flowrelationship. The flap 153 has a surface area smaller than a surfacearea of the opening 152, thereby forming a gap 154 in the body of theflow restrictor 150 when the flap 153 is in a non-deflected positionwithin the opening 152. The flap 153 is shaped so that the gap 154 isnon-uniform.

For certain embodiments, such as that shown in FIGS. 19(b) and 19(c),the flap 153 of the flow restrictor 150 may be shaped such that the gap154 is substantially uniform. Here, the body of the flow restrictor 150has a mechanically reinforced outer portion 151 surrounding an opening152, with the flap 153 positioned in the opening. The flap 153 iscoupled to the outer portion 151 at a side of the opening 152 and maydeflect from the opening 152 due to gas flow through the flow restrictor150. As shown, the flap 153 is shaped and sized such that the gap 154between the outer edge of the flap 153 and the inner edge of the outerportion 151 is substantially uniform. In this case, the width of the gap154 at the flap sides 155 is greater for the example of FIGS. 19(b)-(c)as compared to the width of the gap 154 for the example of FIG. 19(a).As further shown, the overall area or size of the gap between the flapand the outer portion along the plane of the flow restrictor issubstantially similar for the examples shown in each of FIGS. 19(a) and19(b)-(c).

FIGS. 19(d)-(e) depict another embodiment of a flow restrictor 1500having an outer portion 1510 surrounding a flap 1530, similar to otherexamples described herein. However, in this embodiment, the outerportion 1510 encapsulates an insert 1580 which may provide a suitablelevel of mechanical stability for the flow restrictor 1500. Inparticular, the insert 1580 may support the flap 1530 during assembly ofthe flow sensor system (e.g., where the flow conduit may be provided asa snap fit arrangement), and may prevent or reduce the possibility ofbending of the flap 1530. Otherwise, when pressure is applied to theouter portion 1510 during assembly, without such increased stability;the flap 1530 may be undesirably prone to bending which may then lead toinaccuracies in flow measurements. Hence, the insert 1580 may becomposed of a relatively rigid material as compared to the flap 1530 andthe outer portion 1510 of the flow restrictor 1500. For example, theinsert 1580 may comprise a reinforced plastic/polymer, metal, or othersuitable material, and the outer portion 1510 may include a siliconerubber. Alternatively, the outer portion 1510 of the flow restrictor1500 may be composed of a material that is substantially stiffer or morerigid than the flap 1530, without requiring an insert encapsulatedtherein. In certain embodiments, as shown in FIGS. 19(d)-(e), the flowrestrictor 1500 further includes an outer rim 1590 that facilitates theformation of a seal upon assembly of two segments (e.g., halves) of aflow conduit that are connected together.

Accordingly, the flow conduit may be manufactured according to a snapfit configuration where two segments 110 a, 110 b of the flow conduitare connected together to form a larger assembly. For example, FIG.19(e) depicts an up close view showing a connector 900 that provides asnap fit seal against an outer rim 1590 (e.g., made up on a siliconerubber or other elastomeric material) of the flow restrictor 1500 forsegments 110 a, 110 b of the flow conduit upon assembly thereof. Theflow restrictor 1500 may be substantially tapered to a thin neck region1570 adjacent to the outer rim 1590. This thin neck region 1570 may beuseful to minimize or otherwise reduce the possibility for the flap 1530to bend during assembly of the segments of the flow conduit 110 a, 110b. Such bending may be due to torsion that is transferred toward theflap 1530; a relatively thin neck region 1570 may reduce the effects oftorsional transfer during assembly. In general, it may be preferable forthe flap 1530 to be kept relatively straight so as to give rise toconsistent bi-directional flow through the lumen 102. The outer portion1510 may further include chamfers that are tapered toward the flap 1530.Such a tapered shape may be beneficial to help streamline air flowtoward the flap, rather than for more turbulent flow patterns todevelop. While not shown in the figures, the flap 1530 itself may alsobe chamfered, so as to allow for relatively smoother (more laminar) flowthrough the opening. The shape of the tapered (chamfered) surfaces ofthe outer portion 1510 and/or the flap 1530 may provide forcomparatively less flow obstruction than if the surfaces wererectangular or more bulky in nature. Such constructions have been foundto result in more linear pressure-flow rate behavior, particularly atlow flow pressures (e.g., less than 75 Pa).

In particular, the flap 153 (or 1530) has a polygonal or substantiallypolygonal shape with a plurality of flap sides 155 and rounded corners156 defined between at least some of the sides 155. One of the sides 155is hingedly coupled to the outer portion 151 to allow for deflection ofthe flap 153. The opening 152 has a rounded rectangular shape at an endopposite to the end to which the flap 153 is hingedly coupled to theouter portion 151. Two sides 155 of the flap 153 are disposed oppositeto respective rounded corners 157 of the opening 152 such that the gap154 formed between the flap 153 and the outer portion 151 is larger atthe rounded corners 157 of the opening 152. Alternatively, as shown forFIGS. 19(b)-19(c), the flap may be shaped and sized such that the outeredge of the flap and the inner edge of the outer portion extendgenerally parallel to one another, resulting in a substantially uniformgap. As shown in FIG. 20(a), the configuration of the opening 152 andthe flap 153 results in the flow restrictor 150 creating a pressure dropthat varies substantially linearly with respect to the flow rate of gasthrough the lumen at or near the resistance limit for the flow conduit.

As noted above, with respect to obtaining accurate flow readings,certain regions of the flow sensor system may be more sensitive to theaccumulation of water and/or debris than others. The flow restrictor maybe constructed so that water and/or debris are diverted away from moresensitive regions, which may contribute to the overall accuracy of flowdetermination, to other neighboring regions that are less sensitive todetermining the accuracy of flow. Hence, one or more sensitive regionsof the flow restrictor may exhibit a greater level of hydrophobicitythan the neighboring region(s) adjacent to the sensitive region(s).

For example, the flow restrictor 150 may include a material (e.g.,polytetrafluoroethylene) that exhibits a greater level of hydrophobicitythan regions neighboring the flow restrictor, such as the surface of theflow conduit immediately adjacent to the flow restrictor. The flowrestrictor itself may be made up of the hydrophobic material, or theflow restrictor may be coated with the hydrophobic material. As notedabove, the surface of the flow conduit neighboring the flow restrictormay include a plastic or polymeric material that is less hydrophobic (ormore hydrophilic) as compared to the flow restrictor, resulting in wateraccumulation or diversion away from the flow restrictor and toward theneighboring region. Or, the flow restrictor itself may have regionswhich exhibit different levels of hydrophobicity. For example, the flap153 may include a relatively hydrophobic material (e.g.,polytetrafluoroethylene), and the surrounding outer portion 151 may behydrophilic, or less hydrophobic, in comparison to the flap 153.Accordingly, water may tend to accumulate or be diverted away from theflap 153 and toward the neighboring or surrounding outer portion 151,resulting in more accurate pressure/flow readings than might otherwisebe the case.

Flow restrictors in accordance with the present disclosure may be formedby any suitable technique. For example, parts or the entirety of theflow restrictor may be die cut, molded, or formed by another appropriatemethod. In some cases, forming the flow restrictor as a molded part mayhave manufacturing benefits, for example, in producing relativelyinexpensive parts in an accurate and precise manner.

With reference to FIG. 20(b), the flow restrictor 160 according to oneembodiment of the present disclosure comprises a body configured to bedisposed in the lumen 72, 102 of a flow conduit 71, 101. The bodycomprises an outer portion 161 that surrounds an opening 162. Threesimilarly sized and shaped substantially triangular flaps 163, 164, 165are disposed adjacent to each other in the opening 162 and are hingedlycoupled to the outer portion 161 at respective sides of the opening 162.The flaps 163, 164, 165 are sized to have a collective surface areasmaller than the surface area of the opening 162 so as to leave a gap166 between each other when the flaps 163, 164, 165 are in anon-deflected position. The gap 166 is substantially uniform and hasthree equally spaced legs. The flaps 163, 164, 165 are configured todeflect from the opening 162 due to gas flow through the restrictor 160.The amount of deflection of the flaps 163, 164, 165 is variable basedupon the flow of gas through the lumen 72, 102. As shown in FIG. 20(b),the configuration of the opening 162 and the flaps 163, 164, 165 resultsin the flow restrictor 160 creating a pressure drop that varies somewhatlinearly with respect to the flow rate of gas through the lumen 72, 102,but above the preferred resistance limit for the flow conduit.

With reference to FIG. 20(c), the flow restrictor 71, 101 according toone embodiment of the present disclosure comprises a body configured tobe disposed in the lumen 72, 102 of a flow conduit 71, 101. The bodycomprises an outer portion 171 that surrounds an opening 172. Fivedifferently sized and shaped substantially triangular flaps 173, 174,175, 176, 177 are disposed adjacent to each other in the opening 172 andare hingedly coupled to the outer portion 171 at respective sides of theopening 172. In particular, the top flap 173 is broader and shorterwhile the other four flaps 174, 175, 176, 177 are similarly sized andshaped. The flaps 173, 174, 175, 176, 177 are sized to have a collectivesurface area smaller than the surface area of the opening 172 so as toleave a gap 178 between each other when the flaps 173, 174, 175, 176,177 are in a non-deflected position. The gap 178 is non-uniformly shapedand has five differently sized and shaped legs configured in the mannerof a five pointed star. The flaps 173, 174, 175, 176, 177 are configuredto deflect from the opening 172 due to gas flow through the flowrestrictor 170. The amount of deflection of the flaps 173, 174, 175,176, 177 is variable based upon the flow of gas through the lumen 72,102. As shown in FIG. 20(c), the configuration of the opening 172 andthe flaps 173, 174, 175, 176, 177 results in the flow restrictor 170creating a pressure drop that varies substantially linearly with respectto the flow rate of gas through the lumen at or near the preferredresistance limit for the flow conduit.

With reference to FIG. 20(d), the flow restrictor 180 according to oneembodiment of the present disclosure comprises a body configured to bedisposed in the lumen 72, 102 of a flow conduit 71, 101. The bodycomprises an outer portion 181 that surrounds an opening 182. Fourdifferently sized and shaped substantially triangular flaps 183, 184,185, 186 are disposed adjacent to each other in the opening 182 and arehingedly coupled to the outer portion 181 at respective sides of theopening 182. The flaps 183, 184, 185, 186 are sized to have a collectivesurface area smaller than the surface area of the opening 182 so as toleave a gap 187 between each other when the flaps 183, 184, 185, 186 arein a non-deflected position. The top flap 183 is longer while the bottomflap 185 is correspondingly shorter. The side flaps 184, 186 aresimilarly shaped in a manner complementary to the top and bottom flaps183, 185. The gap 187 is non-uniform and has four non-equally spaced andsized legs arranged in opposing large and small substantially V-shapes.The flaps 183, 184, 185, 186 are configured to deflect from the opening182 due to gas flow through the flow restrictor 180. The amount ofdeflection of the flaps 183, 184, 185, 186 is variable based upon theflow of gas through the lumen 72, 102. As shown in FIG. 20(d), theconfiguration of the opening 182 and the flaps 183, 184, 185, 186results in the flow restrictor 180 creating a pressure drop that variessomewhat linearly with respect to the flow rate of gas through thelumen, yet slightly above a preferred resistance limit for the flowconduit.

With reference to FIG. 20(e), the flow restrictor 190 according to oneembodiment of the present disclosure comprises a body configured to bedisposed in the lumen 72, 102 of a flow conduit 71, 101. The bodycomprises an outer portion 191 that surrounds an opening 192. A singlesubstantially triangular flap 193 is disposed in the opening 192 and ishingedly coupled to the outer portion 191 at the top side of the opening192. In some embodiments, the flap may incorporate slits to allow formultiple flap segments. The flap 193 is sized to have a surface areasmaller than the surface area of the opening 192 so as to leave a gap194 between the flap 193 and the outer portion 191 when the flap 193 isin a non-deflected position. The gap 194 is substantially V-shaped andhas a substantially uniform thickness. The flap 193 is configured todeflect from the opening 192 due to gas flow through the flow restrictor190. The amount of deflection of the flap 193 is variable based upon theflow of gas through the lumen 72, 102. As shown in FIG. 20(e), theconfiguration of the opening 192 and the flap 193 results in the flowrestrictor 190 creating a pressure drop that varies non-linearly,somewhat curvilinearly, with respect to the flow rate of gas through thelumen 72, 102, yet above a preferred resistance limit for the flowconduit.

With reference to FIG. 20(f), the flow restrictor 200 according to oneembodiment of the present disclosure comprises a body configured to bedisposed in the lumen 72, 102 of a flow conduit 71, 101. The bodycomprises an outer portion 201 that surrounds an opening 202. Fourdifferently sized and shaped substantially triangular flaps 203, 204,205, 206 are disposed adjacent to each other in the opening 202 and arehingedly coupled to the outer portion 201 at respective sides of theopening 202. The flaps 203, 204, 205, 206 are sized to have a collectivesurface area smaller than the surface area of the opening 202 so as toleave a gap 207 between each other when the flaps 203, 204, 205, 206 arein a non-deflected position. The gap 207 is substantially uniform andhas a substantially X-shape. The top and bottom flaps 203, 205 aresymmetrically shaped with each other and are comparatively shorter andbroader and the right and left flaps 204, 206 are symmetrically shapedwith each other and are comparatively longer and narrower. The flaps203, 204, 205, 206 are configured to deflect from the opening 202 due togas flow through the flow restrictor 200. The amount of deflection ofthe flaps 203, 204, 205, 206 is variable based upon the flow of gasthrough the lumen 72, 102. As shown in FIG. 20(f), the configuration ofthe opening 202 and the flaps 203, 204, 205, 206 results in the flowrestrictor 200 creating a pressure drop that varies substantiallylinearly with respect to the flow rate of gas through the lumen 72, 102at or near the preferred resistance limit for the flow conduit 71, 101.

According to one embodiment of the present disclosure, the body of theflow restrictor 150, 160, 170, 180, 190, 200 comprises a hydrophobicmaterial in order to limit or prevent the accumulation of moisture anddebris on the body of the flow restrictor 150, 160, 170, 180, 190, 200.In particular, the body is formed from polytetrafluoroethylene (PTFE) ofthe type sold under the brand name TEFLON®. Alternatively, the body maybe made from polyethylene terephthalate (BoPET) of the type sold underthe trade name MYLAR®. It is to be appreciated that the flow restrictor150, 160, 170, 180, 190, 200 may be formed from any material known to besuitable to those having ordinary skill in the art. The outer portion151, 161, 171, 181, 191, 201 comprises a mechanical reinforcement toprevent deflection of the body outside of the at least one flap,maintain the flow restrictor 150, 160, 170, 180, 190, 200 in a secureposition, and facilitate rigid and repeatable assembly of the flowconduit 71, 101. The mechanical reinforcement may comprise at least onelaminate layer applied to the outer portion 151, 161, 171, 181, 191, 201and/or a stiffener coating.

In accordance with aspects of the present disclosure, as noted above,the flow restrictor 150, 160, 170, 180, 190, 200 may be tune-ablyconstructed so as to exhibit a preferred relationship (e.g., linear,non-linear, curvilinear, quadratic, etc.) between pressure drop andflow. It can be appreciated that a number of factors contribute to howthe pressure drop and flow may vary with respect to one another, such asthe shape(s), size(s) and material(s) from which the flow restrictor150, 160, 170, 180, 190, 200 is constructed. In the case of the flowrestrictor 150 of FIGS. 19(a)-(c), the height of the flap 153, the widthof the flap 153, the size of the gap 154, and other factors maycontribute to the overall pressure-flow relationship of the flow sensor.For example, a flap 153 having an approximately similar height and widthand a gap 154 of sufficient size may result in a substantially linearpressure-flow relationship. In some cases, the number of flaps maycontribute to the curvature in the relationship between pressure dropand flow, for example, less flaps may give rise to a more linearresponse. The type of material(s) from which the flow restrictor 150,160, 170, 180, 190, 200 is composed of may also contribute to theoverall pressure-flow relationship. For example, for a given flow ratethrough the lumen 101, use of a flow restrictor 150, 160, 170, 180, 190,200 made up of a more rigid material may result in a greater pressuredrop as compared to use of a flow restrictor 150, 160, 170, 180, 190,200 made up of a more flexible material. Or, in some instances, theshape of the flap(s) may contribute to the manner in which pressure dropvaries with flow. For instance, the example flow restrictor 190 of FIG.20(e) resulted in a relatively quadratic, non-linear pressure-flowprofile, whereas the example flow restrictor 150 of FIG. 20(a) resultedin a substantially linear pressure-flow profile. Accordingly, byadjusting various aspects of the flow restrictor 150, 160, 170, 180,190, 200 (e.g., shape, size, material, thickness, amongst others), thepressure-flow response profile may be appropriately configured todesired specifications.

FIG. 21(a) illustrates the effects of changing the thickness of thevariable orifice flow restrictor and the size of the opening on therelationship between the pressure drop created by the flow restrictorand the flow rate of gas through the lumen. As shown, adding thickness(hence, further mechanical reinforcement) to the flap tends to increasethe pressure drop created by the flow restrictor to a level past theresistance limit of the flow conduit. This effect can be ameliorated byincreasing the size of the opening by a suitable degree. Accordingly,certain flow restrictors with an enlarged opening may perform better atachieving pressure drops at or near the resistance limit of the flowconduit for a given flow rate of gas regardless of material thickness.In various embodiments, flow restrictors may be constructed so as tovary in thickness along their length, so suit the desired pressure-flowrelationship. FIG. 21(b) illustrates the effects of providing sharpcorners or rounded or fileted corners on the flap on the relationshipbetween the pressure drop created by the flow restrictor and the flowrate of gas through the lumen. As shown, fileting the corners of theflap slightly reduces the pressure drop created by the flow restrictorat a given flow rate, which can be helpful in achieving a pressure dropwithin the resistance limit of the flow conduit.

According to one particular embodiment of the present disclosure, theflow restrictor 150, 160, 170, 180, 190, 200 is appropriately sized toextend across the lumen 72, 102 of the flow conduit 71, 101 and has amaterial thickness of approximately 5-7 mil. The approximate surfacearea of the opening 152, 162, 172, 182, 192, 202 through the flowrestrictor 150, 160, 170, 180, 190, 200 is between approximately0.01-0.1 square inches (e.g., 0.2-0.06 square inches) and theapproximate surface area of the single flap or combined surface areas ofthe multiple flaps is between approximately 0.01-0.5 square inches(e.g., 0.1-0.3 square inches).

With reference to FIGS. 1-18, according to an embodiment of the presentdisclosure a resuscitation system for assisting ventilation is provided.The system comprises a flow conduit 21, 41, 61, 71, 101 having a lumen22, 42, 62, 72, 102 defined therein and a processor 145. The processor145 (optionally located in the cable connector and/or other portions ofthe resuscitation system) is configured to receive a first signalrepresenting a first pressure at a first region of the flow conduit 21,41, 61, 71, 101, receive a second signal representing a second pressureat a second region of the flow conduit 21, 41, 61, 71, 101, determine atleast one of flow rate and volume of gas flowing through the lumen 22,42, 62, 72, 102 of the flow conduit 21, 41, 61, 71, 101 based on thefirst and second signals, and output a feedback signal for a user and/ormachine to adjust gas flow through the lumen 22, 42, 62, 72, 102 of theflow conduit 21, 41, 61, 71, 101 based on at least one of the determinedflow rate and volume of gas flowing through the lumen 22, 42, 62, 72,102.

With reference to FIGS. 16-18, according to an embodiment of the presentdisclosure a connector 113 for establishing communication between anysuitable medical devices (e.g., between a sensor and a patient monitor)is provided. The connector 113 comprises a housing 138 configured to beremovably coupled to a medical device, a plurality of signal conductors144 through an interior region of the housing 138, and a signal contactpad 141 having a plurality of conductive elements 143 arranged in aconcentric pattern. The conductive elements 143 are in electricalcommunication with the plurality of signal conductors 144 and areconfigured to be placed in electrical communication and removablycoupled to the medical device. As discussed above, for variousembodiments, the connector is provided as a reusable component connectedto a medical device monitor, where the reusable connector is configuredto be removably coupled to a sensor provided as a disposable component,to establish electrical communication between the medical device monitorand the sensor. While the connector may be used to establish electricalcommunication between a flow sensor and a ventilation flow monitor, inaccordance with embodiments described herein, the connector may be usedfor other appropriate sensors and/or devices, such as for example, pulseoximeter, muscle pH sensor, carbon dioxide sensor, blood pressuresensor, ECG sensor, chest compression sensor, etc.

Flow sensor systems described herein may be used not only with automatedmechanical ventilation systems and manual ventilation (bagging) systems,but also may be used with spontaneously breathing patients. For example,the patient may have a mask to which the flow sensor may be coupled andexposed to the ambient atmosphere. In such cases, because the flowsensor is used in an open system that is exposed to ambient air, theflow sensor does not require two separate absolute pressure sensors.That is, the pressure at the region within the lumen of the flow conduitexposed to the ambient atmosphere is already known to be approximatelyatmospheric pressure (which can be determined when the flow sensorsystem is turned on prior to use with a patient or by calculating thepressure value upon which the pressure readings oscillate). Accordingly,a single absolute pressure sensor is provided to determine the pressureat the other region within the lumen of the flow conduit on the oppositeside of the flow restrictor. As a result, flow sensor systems inaccordance with the present disclosure may employ only a single pressuresensor for measuring the absolute pressure at a patient side region ofthe lumen within the flow conduit.

For instance, FIGS. 38 and 39 illustrate a flow sensor system 400 inaccordance with an embodiment of the present disclosure thatincorporates a single absolute pressure sensor 431 for measuring theabsolute pressure in a first, patient side, region 403 of the lumen 402within the flow conduit 401. The flow sensor system 400 comprises theflow conduit 401 that defines the lumen 402 allowing for the passage ofgas through the flow conduit 401 from a ventilation source, such as amanual ventilation bag or automated ventilation system, to a patient.The flow conduit 401 is configured to allow gas flow between the first,patient side, region 403 and a second region 404. The flow conduit 401comprises a body extending from a first end to a second end of the flowconduit 401. The body has a hollow interior, which defines the lumen402.

A flow restrictor 405, which can be a flow restrictor according to anyof the above-described embodiments, is disposed within the lumen 402 ofthe flow conduit 401 between the first region 403 and the second region404 so as to extend across all or a portion of the lumen 402 in order toobstruct the flow of gas through the lumen between the first region 403and the second region 404 and create a pressure drop in the flow, whichcan be measured to calculate the absolute pressure of the gas passingthrough the flow conduit 401 in the first, patient side, region 403 ofthe lumen 402.

As shown, the flow sensor system 400 comprises a single absolutepressure sensor 431 disposed adjacent to the first region 403 of theflow conduit 401. The single absolute pressure sensor 431 is configuredto measure a pressure due to gas flow in the first region 403 of theflow conduit 401. According to one particular embodiment of the presentdisclosure, the absolute pressure sensor 431 is a miniatureelectro-mechanical systems (MEMS) devices configured to sense anabsolute pressure within the respective region 403 of the lumen 402,such as the BME 280 sensor or BMP 200 sensor manufactured by BoschSensortec GmbH. It is to be appreciated, however, that the absolutepressure sensor 431 may be of any type known to be suitable to thosehaving ordinary skill in the art capable of sensing a pressure withinthe region 403 of the lumen 402. Or, as further provided herein, ratherthan absolute pressure sensors, differential pressure sensors may beemployed for determining the pressure drop between regions on opposingsides of the flow restrictor.

The absolute pressure sensor 431 is in communication with the lumen 402in the first, patient side, region 403 in order to measure the absolutepressure of the gas flowing through the lumen 402 in the region 403. Theabsolute pressure sensor is mounted on and connected to a circuit board410 disposed on the flow conduit 401 such that the absolute pressuresensor 431 is disposed in a chamber 414 provided in the upper surface ofthe flow conduit 401. The chamber 414 is configured to house and supportthe pressure sensor 431 adjacent to the lumen 402 of the flow conduit401. The chamber 414, and thus the pressure sensor 431, is in fluidcommunication with the lumen 402 via an opening 419 defined in andextending through the flow conduit 401 between the lumen 402 and thechamber 414. A membrane, diaphragm membrane, or a rolling diaphragm asdiscussed above with respect to various other embodiments of the presentdisclosure may be provided to prevent moisture, debris, and possibly gasfrom passing to the chamber 414 from the lumen 402.

The circuit board 410 may be secured to the flow conduit 401 by anysuitable manner, for example, via mechanical attachment (e.g., welding,adhesive, interference fit, complementary coupling features, etc.). Withreference to FIG. 39, a ring hole 415 may be provided in the top surfaceof each of the flow conduit 401 around the chamber 414. A sealant oradhesive may be placed within the ring hole 415 to secure the circuitboard 410 to the upper surface of the flow conduit 401. The uppersurface of the flow conduit 401 also comprises upwardly extending pins421. The pins 421 are received in pin holes (not shown) extendingthrough the circuit board 410 to assist in positioning and securing thecircuit board 410 on the upper surface of the flow conduit 401.

An adapter 412, which may be the same as the adapter discussed abovewith reference to the embodiment of FIGS. 6-18, may be disposed on anupper surface of the circuit board 410 and is electronically connectedto the circuit board 410. The flow sensor system 400 also comprises acover 411 for the circuit board 410. The cover 411 is positioned on theupper surface of the flow conduit 401 over the circuit board 410. Boththe circuit board 410 and the cover 411 are shaped to correspond to theshape of the upper surface of the flow conduit 401 in order to fit onthe flow conduit 401 and hold the circuit board 410 in place. The cover411 is configured to hold the adapter 412 and allow the adapter 412 toextend therethrough so that the adapter 412 can establish electroniccommunication with a connector, such as the connector 113 discussedabove with reference to the embodiment of FIGS. 6-18. The cover 411comprises an alignment disk 435 positioned on the top of the cover 411.As discussed above, the alignment disk 435 is configured to provide aguide for positioning the connector so that the connector may beelectronically connected to the adapter 412 and to limit lateralmovement of the connector once the connector is connected to the flowconduit 401. Snap arms 409 may extend from the upper surface of the flowconduit 401 to engage the connector to maintain the connector in aconnected position with the cover 411 and the adapter 412, as discussedabove. Though, the connector may be engaged with the conduit by anyother suitable method, for example, interference fit, magnetic coupling,etc.

In another embodiment of the present disclosure, as shown in FIGS.57-59(a)-(b), the flow sensor system 100 includes chamber inserts 600and membranes 640 disposed within respective recesses 650 on either sideof the flow restrictor 105, so as to form corresponding chambers 610 foreach pressure sensor. It is noted that, for this embodiment, thepressure sensors are provided on the lower side of the circuit board 110and, hence, are not expressly shown in FIGS. 57-59(a)-(b). Also notexpressly shown in these figures are optional heating elements (e.g.,electrical resistors) located adjacent to the pressure sensors. Similarto other filter layers described herein, the membranes 640 may be madeup of a gas permeable, breathable, hydrophobic material that allow forthe passage of gas through the membrane 640 while also providing abarrier that prevents or otherwise obstructs the passage of liquidmoisture and debris through the membrane 640. The body of the flowconduit 101 is shaped so as to include reservoirs 630 on either side ofthe flow restrictor 105, for trapping and collection of water,particulate matter and/or other debris.

FIG. 59(a) shows a closer view of the chamber insert 600, and FIG. 59(b)depicts a cross-sectional view of the chamber insert 600 positionedwithin a corresponding recess 650 of the flow sensor system. Whensuitably positioned within the recess 650, a chamber 610 is formedaround the respective pressure sensor of the circuit board 110. Whilenot expressly shown in FIG. 59(b), the pressure sensor is located withinthe chamber 610 and mounted on the circuit board 110 so as to face in adownward direction, toward the opening 608. The opening 608 allows forgas to pass there through having traveled across the gas permeablemembrane 640 between the lumen 102 of the flow conduit 101 and thechamber 610. Further, the chamber 610 may be shaped so as to allow asnug fit for the pressure sensor therein, with little air volume betweenthe pressure sensor and the surface of the chamber insert 600. By sizingthe chamber 610 to approximate that of the pressure sensor (e.g.,minimizing the amount of excess chamber volume), the total amount of airfor the heating elements to transfer heat is reduced, leading to anoverall enhanced heating effect as compared to instances where thechamber is sized to enclose larger volumes of air.

In this embodiment, the opening 608 has a ribbed portion 609 that isstructured so as to form another reservoir 620 adjacent to the opening608 and the membrane 640. This reservoir 620 provides a small pocket fortrapping and collecting liquid, debris and/or other potential sources ofcontamination that might otherwise interfere with pressure sensorreadings. For instance, the reservoir 620 may serve as a destination forwater vapor having traveled from the flow lumen 102 and passed throughthe membrane 640 to condense or settle. Salt or other particulates thatare able to pass through the membrane 640 may also collect at thereservoir 620. The ribbed portion 609 is slightly tapered in a mannerthat directs liquid or other debris from the opening 608 toward thereservoir 620.

In some embodiments, to encourage water and/or other sources ofcontamination away from the chamber 610 within which the pressure sensoris located and, for example, toward the reservoir 620, certain portionsof the chamber insert 600 may exhibit varying levels of hydrophobicity.As an example, the inner surface 608 a of the opening 608 may include amaterial and/or coating that exhibits a greater level of hydrophobicityas compared to the outer surface 609 a of the reservoir 620. Forinstance, the outer surface 609 a of the ribbed portion 609 and/or thereservoir 620 may include a material and/or coating that is hydrophilicin nature (e.g., contact angle less than 90 degrees). As noted above,heating elements may be provided within or adjacent to the chambers 610(e.g., next to the pressure sensors), further reducing the possibilityof condensation which could otherwise give rise to measurement errors.

As illustrated, the chamber insert 600 includes additional ribbedportions 602, 604, 606 formed as rings around the body of the chamberinsert and that protrude therefrom so as to provide an enhanced sealand/or mechanical stability in engagement between the chamber insert 600and other portions of the flow sensor system. In particular, the chamberinsert 600 includes an upper ribbed portion 602 that protrudes upwardfrom the body of the chamber insert 600 in a manner that sealinglyengages with the lower surface of the circuit board 110. The chamberinsert 600 also includes a lower ribbed portion 604 that protrudesdownward from the body of the chamber insert 600 to sealingly engagewith a corresponding region of the flow conduit 101. And further, thechamber insert 600 includes a lateral ribbed portion 606 that protrudeslaterally from the chamber insert body to sealingly engage with anothercorresponding region of the flow conduit 101.

For convenient and proper assembly of the flow sensor, similar to otherembodiments described herein, various parts may include appropriatelypositioned protrusions and recesses for insertion/assembly thereof. Forexample, as shown in FIG. 58, the cover 111 includes a pin 700 thatinserts into a hole 704 of the circuit board 110, and further insertsinto a hole 702 of the flow conduit 101. Further, as shown in FIGS. 57and 59(a), the chamber insert 600 may include a keying arm 601, which isconstructed for insertion in a corresponding recess 632 of the flowconduit 101. The combined keying arm 601 and recess 632 assists a userin proper assembly of the flow sensor system, for example, so that theinsert 600 is not inserted upside down.

FIGS. 60-62(a)-(b) depict another embodiment of a flow sensor system 100having chamber inserts 800 that include diaphragm membranes 820 similarto those of other embodiments described herein. It is noted that, forthis embodiment, the components of the flow conduit 101, circuit board110, cover 111 and adapter 112 are the same as that described for theembodiment of FIGS. 57-59(a)-(b), with the exception of the chamberinserts 800 and absence of the gas permeable membranes 640. Inparticular, the chamber inserts 800 of this embodiment have replaced thechamber inserts 600 and membranes 640 of FIGS. 57-59(a)-(b). Indeed, therespective chamber inserts 600 and 800 may be interchangeable.Accordingly, upon assembly of the flow sensor, the chamber inserts 800are disposed within respective recesses 650 on either side of the flowrestrictor 105 so as to form corresponding chambers 810 for eachpressure sensor. In this example, the diaphragm membrane 820 provides asubstantial barrier between the flow conduit 101 and the respectivechamber 810, allowing for pressure changes within the lumen 102 withinthe immediate vicinity of the diaphragm membrane 820 to be suitablydetermined. In various embodiments, the diaphragm membrane 820 iscomposed of a material that is impermeable to gas. Also, the body of theflow conduit 101 is shaped so as to include reservoirs 630 on eitherside of the flow restrictor 105, for trapping and collection of water,particulate matter and/or other debris. FIG. 62(a) shows a closer viewof the chamber insert 800, and FIG. 62(b) depicts a cross-sectional viewof the chamber insert 800 positioned within a corresponding recess 650of the flow sensor system 100. When suitably positioned within therecess 650, a substantially sealed chamber 810 is formed around therespective pressure sensor of the circuit board 110. The diaphragmmembrane 820, formed of an impermeable material and equipped with asuitably patterned structure, then allows for pressure equalizationbetween the lumen 102 of the flow conduit 101 and the space withinchamber 810 where the pressure sensor is located. Accordingly, pressurechanges of the region of the lumen 102 immediately outside of thechamber 810 can be suitably determined by the pressure sensor locatedwithin the chamber 810, while at the same time minimizing or otherwisereducing the travel of water vapor and/or other gases into the chamberin a manner that would introduce unwanted error in the pressuremeasurements. By sufficiently protecting the pressure sensor fromsignificant exposure to the external environment, other methods foraverting water accumulation (e.g., via condensation) within the chamberand, hence, ensuring accuracy of pressure sensor measurements, such asimplementation of the resistive heating element(s) (which uses a smallamount of power output from the system) may not be required.

As discussed above, it may be desirable for the flow sensor system 100to be used in environments of varying pressure, for example, lowaltitude and high altitude. However, if the chamber 810 is completelysealed, the flow sensor system may succumb to inaccurate pressure-flowreadings when subjected to large variations in environmental pressure.The rolling diaphragm configuration described above may be employed,though, another method of compensating for such situations is byincorporating a slight opening 822 within the diaphragm membrane 820, asillustrated in FIG. 62(a). The presence of this opening 822 allows forslow travel of gas between the chamber 810 and the lumen 102.Accordingly, when the flow sensor 100 system moves from a high pressuresystem to a low pressure system, or vice versa, the pressure between thechamber 810 and the lumen 102 can come to a suitable equilibrium,without detrimental effect to flow sensor operation. However, the sizeof the opening 822 is small enough such that immediate pressurefluctuations due to flow through the sensor will still be captured in areliable and suitably accurate manner. As a result, the flow sensorsystem 100 may be effective in its usage both at sea level (i.e., highpressure environment) and at high altitudes (i.e., low pressureenvironment).

The chamber insert 800 may include ribbed portions 802, 804, similar tothat discussed above with respect to other embodiments. Such ribbedportions may provide an enhanced seal and/or mechanical stability inengagement between the chamber insert 800 and other portions of the flowsensor system 100, such as the circuit board 110 and the flow conduit101.

In addition to processing pressure signals to determine particular flowparameters, such as flow rate and flow volume, flow sensor systems inaccordance with certain embodiments may be used to provide additionalpatient information to assist other aspects of the resuscitationprocess. For example, the pressure signal recorded by the pressuresensor(s) may be used to detect or otherwise estimate the rate and/ordepth of chest compressions. When CPR chest compressions are applied toa patient, a small amount of airflow is generated due to the force ofcompressions on the chest of the patient. This airflow can be measuredby the flow sensor system and, hence, can be used to determine whetherchest compressions are being applied, the rate at which chestcompressions are occurring, and the relative depth or force of CPRcompressions.

FIG. 40 depicts a graph that plots how flow rate changes with time aschest compressions are applied to the patient. Flow rates generated fromCPR chest compressions can be clearly distinguished from flow ratesgenerated from bagged breaths given to the patient. Thus, the number ofchest compressions applied can be easily counted by the system and/oruser. In some cases, the overall minute ventilation provided to bepatient may be characterized from compressions, which may indicate thatfewer ventilation breaths may be required. As shown in FIG. 40, chestcompressions produce a rate of airflow that is readily apparent andmeasurable by the flow sensor system. Further, the flow rate producedfrom chest compressions, while easily observable, is substantiallysmaller than the flow rate produced from a bagged breath. Hence, it ispossible to determine the rate of chest compressions applied to thepatient. Accordingly, the number of chest compressions may also becounted or otherwise tracked by a user and/or system, for example, toensure that the rescue process is in adherence to preferredresuscitation protocols. In some embodiments, an accelerometer may beused to detect CPR chest compressions and/or ventilation rate. Sternaldisplacement due to compressions has a high frequency leading edge andis initially negative (compression), while the ventilation cycle has aleading edge that is approximately an order of magnitude lower infrequency (0.5 Hz vs. 5 Hz) than the compression cycle, and is positive(chest rising due to lung inflation). Thus, ventilations can bedistinguished from compressions, e.g., using a bandpass filter in thesoftware detection algorithm. In situations where compressions are givento the patient during the course of a ventilation, the system may beable to distinguish between flows that have arisen due to ventilationversus compression. Such a distinction may be beneficial so that flowarising due to a compression is not mistakenly counted as an additionalventilation when determining ventilation rate. For example, in countingthe number of ventilations that have occurred, there may be arequirement for the flow volume to meet a particular threshold (e.g.,100 mL) for a positive ventilation detection to be registered,otherwise, the system may be configured such that flow volumes below thethreshold are not sufficient enough to be counted as “true”ventilations, but may simply be due to other activities (e.g., chestcompressions, movement of the patient).

A common protocol employed by emergency services during resuscitation isa 30:2 protocol, where 30 chest compressions are applied for every 2positive ventilation breaths. An alternative protocol is for a patientto be ventilated continuously at a rate of 8-10 positive breaths perminute concurrently with synchronized chest compressions (e.g., applyinga positive ventilation breath during the upstroke phase of chestcompression), for example, when the airway is in place. Thus, dependingon the resuscitation protocol employed, the system may provide anindication of the number of chest compressions that have been applied soas to guide/coach the user in applying ventilations at the appropriatetime(s), and/or to coordinate timing of positive pressure breathsprovided by an automated ventilation system. For example, if a 30:2compressions to ventilations protocol is employed, the flow sensorsystem, optionally in combination with a chest compression sensor (e.g.,accelerometer, motion sensor), may be used to detect whether chestcompressions are applied. The system may further count the number ofapplied compressions (e.g., based on pressure data collected from theflow sensor and/or accelerometer data collected from a chest compressionsensor) and then alert the rescuer to give breaths at the appropriatetimes. Alternatively, in another example, if a continuous ventilationprotocol is employed, a countdown timer and/or a count up timer based onelapsed time may be used to continuously prompt the user and/orventilation apparatus to give a breath every 6-8 seconds or anotherrate, according to whatever target rate is provided by the protocol. Or,the system may simply prompt the user to apply a ventilation accordingto a timed schedule (e.g., every 15-20 seconds, approximately every 18seconds for 30 compressions at 100 compressions/minute).

The system may have a user interface that allows the preferredventilation protocol to be applied. For example, a button or othercontrol may be actuated so as to toggle or otherwise select betweenventilation protocols so that the rescuer is appropriately guidedthrough the ventilation portion of the resuscitation process. Though, itis not required for a user to actively select which ventilation protocolis applied. For example, in some embodiments, because the flow sensorsystem may detect both ventilations and chest compressions, theventilation protocol may be automatically detected and, hence, beautomatically selected without need for an express user selection. Thatis, once ventilations are detected, a ventilation dashboard or otherfeedback mechanism (e.g., visual, audio, haptic) configured to provideguidance to the user in administering proper ventilations (according tothe appropriate ventilation protocol) may be launched.

In some embodiments, it can be beneficial to time the CPR compressionssuch that the CPR compression does not occur at the same time as aventilation. The system may time compressions provided by manual orautomated CPR compressions via the pressure signal and/or anaccelerometer. Based on information from the accelerometer or pressuresignal in combination with data from the ventilation assembly, thesystem determines whether a timing for a ventilation overlaps with atiming for a CPR compression cycle and provides an indication to therescuer if a ventilation is being delivered during a compression cycleso the rescuer can delay either the compression or the ventilation sothat they do not overlap. As noted above, the system may guide therescuer in providing a positive pressure breath during the chest recoilphase of compressions so that air is more easily able to travel into thelungs due to the negative intrathoracic pressure induced by chest wallrecoil.

In some embodiments, artifacts produced due to chest compressions may befiltered out of the flow rate and/or volume signal, allowing chestcompressions to continue while also observing or determining anestimated, substantially error-free flow/volume signal. For example,since the rate of chest compressions may be determined via anaccelerometer and/or pressure signal, the system may be configured tofilter out artifacts due to the compressions so as to calculate and/ordisplay a filtered representation of the flow rate and/or flow volume.In various embodiments, systems and methods for filtering out chestcompressions from a flow signal may be similar to those described inUS2013/0184600, entitled “Systems and Methods for Filtering ECGArtifacts,” which is hereby incorporated by reference in its entirety.

The filtering algorithm may be a time domain filter. Additionally, thefiltering algorithm may be adaptive such that it identifies thedifferent artifacts created by different rescue workers applying chestcompressions, or different artifacts resulting from rescue workerfatigue, and adjusts the filter accordingly. In various examples, thefilter may be a time domain filter, a Kalman filter, an autoregressivemoving average (ARMA) filter, an adaptive notch filter, or atemplate-based filter. In one example, a Kalman filter may be used topredict the artifact to be subtracted from the flow data in acontinuously adaptive process. According to one embodiment, a heterodyneprocess is used to filter out the compression artifact by filtering thecompression artifact in time with a carrier signal. The carrier signalis created by a local oscillator and set to be close in frequency to thefrequency of the compression rate. The heterodyne process may be used tomodulate the amplitude of the artifact.

In certain embodiments, a continuous filter may be used to filter outartifacts from the flow data. The continuous filter may be synchronizedto the chest compressions. In one example, one or more notch filters areused to filter out artifacts from ECG data. When multiple notch filtersare used to remove the compression artifacts, the center frequency ofthe notch filter can correspond to the chest compression rate or two ormore times that chest compression rate (e.g., harmonics of the chestcompression rate). The chest compression rate may be determined usingsensor data (including, but not limited to pressure sensors, impedancesensors, accelerometers, motion sensors, or other types of sensors),data provided by an automatic electro-mechanical chest compressiondevice, or data derived from a calculation of compression rate based onthe incoming raw pressure data. In one example, two filters are set tothe compression frequency, two filters are set to the first harmonic ofthe compression frequency (where the first harmonic is equal to twotimes the compression frequency), and one filter is set to the secondharmonic of the compression frequency (where the second harmonic isequal to three times the compression frequency). Optionally, additionalfilters may be used to filter out higher harmonics of the compressionfrequency. In another example, the center frequency of the notch filtercorresponds to the most prominent frequency of the artifact.

In some embodiments, the flow sensor system may be used to detect thetype of ventilations that are applied to the patient, or whether thepatient is breathing spontaneously. Based on the profile of pressureand/or flow, it can be determined whether the type of ventilation is dueto manually applied bagged breaths, automatically applied ventilatorbreaths or spontaneous breaths by the patient. For example, informationprovided from the flow sensor system may be used to determine whetherbreaths are generated via positive or negative pressure ventilation.Positive pressure ventilation involves breaths provided from automaticventilators and manual bag valve masks, which supply a positive pressureat the airway opening to push air into the lungs. Negative pressureventilation occurs in spontaneously breathing patients where thediaphragm creates a negative intrathoracic pressure to draw air into thelungs.

FIG. 41 depicts a series of graphs that show the absolute pressure,pressure differential and flow rate detected over time by the flowsensor system for a spontaneously breathing patient. Such a flow profilemay also be indicative of a patient who is experiencing agonalrespiration, which is generally characterized by an abnormal pattern ofbreathing and may include gasping, labored breathing, accompanied byirregular vocalization and/or myoclonus. In a spontaneous breath,because air is drawn in due to negative pressure generated by downwardmovement of the diaphragm, the absolute pressure senses an initialdecrease during inspiration, followed by an increase in pressure duringexpiration.

In some cases, mere detection of a negative pressure may not beconclusive that spontaneously breathing is occurring; for example,incidental jostling or movement of nearby equipment may cause a negativepressure signal to be detected. Hence, to provide greater confidence ofspontaneous breathing, it may be useful to set a minimum threshold offlow rate/volume (e.g., flow volume thresholds of at least 50 L, atleast 100 mL, at least 150 L, etc. and/or flow rates of at least 5L/min, at least 10 L/min, etc.), in combination with a negative pressurechange. For example, when the system detects an initial negativepressure change and a threshold level of flow rate or volume, the systemmay provide an indication to the rescuer or other device that thepatient may be undergoing spontaneous breathing. This information, whilenot conclusive, may be further useful in providing a rescuer with anindication that the patient may be experiencing return of spontaneouscirculation (ROSC). For example, the system may provide a display to therescuer of “Possible ROSC” and/or may provide appropriateinstructions/guidance. To determine whether ROSC has actually occurred,other parameters may need to be considered, such as ETC02, ECG signal,pulse detection, pulse oximetry, etc.

FIG. 42 depicts a series of graphs similar to that shown in FIG. 41, yetfor a patient receiving positive pressure ventilation with a ventilator.Here, both absolute pressure sensors are increased above atmosphericpressure for both inspiration and expiration. The pressure waveform isfurther characterized by a plateau at the height of the ventilatorbreath, which is distinct from a positive pressure breath given bymanual ventilation.

Similarly, FIG. 43 shows similar graphs for a patient receiving manual(bagged) ventilation breaths. In this particular graph, interposedbetween the two large manual ventilation peaks are a number of smallerpeaks indicative of chest compressions. In bagged breathing, bothpressure signals are increased above atmospheric pressure for bothinspiration and expiration. In this respect, both manual and automatedventilation breaths are easily distinguishable from spontaneous breathsin that they are positive pressure breaths. Though, it can beappreciated that the shape of the manually administered breath issubstantially different than that for a breath given by a typicalautomated ventilator. For example, the automated ventilator breath showsa more regular pressure/flow profile, including a plateau in pressure,which is not the case for the administered breath, which is moreirregular in nature.

By determining the type of breath that is occurring, rescuers can bealerted whether the patient has begun spontaneous breathing and adjustthe treatment protocol accordingly. For instance, for a spontaneouslybreathing patient, the rescuer may adjust how much additional ventilatorsupport is necessary to give above what the patient is generating ontheir own. That is, when the patient is spontaneously breathing, theamount of pressure support assisted by manual or automated ventilationmay be appropriately reduced. For example, the better the patient isable to breathe, the less pressure support may be required by positivepressure ventilation.

Further, as noted above, spontaneous breathing, while not fullyconclusive, may be helpful evidence in determining whether the patienthas achieved ROSC. Such information may be considered during an analysisof whether or not to administer a defibrillating shock to the patient.For example, if spontaneous breathing is detected, the rescuer or systemmay be triggered to perform a series of checks to determine if thepatient has achieved or is likely to achieve ROSC. If ROSC has beenachieved, then it may be decided that a shock should not be given. Suchinformation may also be relevant for code review in evaluating whetherrescuers were performing quality CPR. EMS rescuers are typicallyevaluated for how well they each performed CPR, whether or not ROSC hasoccurred. However, when ROSC has occurred in a patient, it may bedetermined that CPR may no longer be needed, hence, it may be preferablethat EMS rescuers not be evaluated for their quality of CPR during ROSC.Thus, using techniques described herein, evidence of ROSC may beconsidered for determining whether EMS rescuers are evaluated forquality of CPR during the time period in which ROSC may have occurred.When ROSC is likely to have occurred, the code review may reflect thatpossibility and, in some cases, the score of EMS rescuers during thetime in which ROSC may have occurred may be withheld from the overallevaluation.

Additionally, when a patient is experiencing spontaneous and/or agonalbreathing, yet still receiving positive pressure breaths, the flowsignal for the positive pressure breath may be inaccurate. Hence, when aspontaneous breath is detected at or around the time in which a positivepressure breath is administered, the flow parameters for that particularbreath may be omitted or otherwise removed from the display or reportprovided to a user interface or other device associated with theresuscitative effort.

FIG. 44 provides a flow chart illustrating an embodiment of the processthrough which a system may utilize information provided from the flowsensor. As shown, the system may detect whether flow is occurringthrough the conduit based on whether a threshold flow rate or volume hasbeen met. If flow has been detected, then a user interface or displayprovided by a device of the system or monitor thereof, may enter into amode that accounts for ventilation parameters. For example, in responseto flow detection, the device may produce a ventilation dashboarddisplayed on a screen thereof. In some embodiments, an overall CPRdashboard may be displayed, which has a chest compression dashboardportion and a ventilation dashboard portion, as appropriate for the typeof treatment(s) to be provided.

The ventilation dashboard may display a number of parameters, such asindicia showing the flow rate and/or volume detected from a breath. Thesystem may further determine what type of breath is being provided, forexample, spontaneous or by positive pressure ventilation (e.g., manuallygiven or automated breath). If ventilations are not detected, the systeminfers that manual ventilations are not being given to the patient, sothen the system refrains from providing prompts to administer manualventilation breaths. Though, if ventilations are detected, then thesystem determines whether the ventilation breaths are generated manually(e.g., from bag ventilation) or mechanically (e.g., from an automatedventilator). If the system determines that the breaths are beingadministered mechanically, then the system refrains from providingprompts for a user to administer manual ventilation breaths. Though, ifthe system determines that the breaths are produced manually, then thesystem then continues to prompt the rescuer to administer breathsaccording to the appropriate treatment protocol.

In certain embodiments, as further shown in FIG. 44, for patients whoare able to breathe spontaneously, the system may be configured to causepositive pressure breaths to be synchronized with spontaneous breaths.It may be preferable for a positive pressure breath to be administeredto a patient simultaneously during the beginning of an inspiratorybreath, so that the gas more readily enters the lungs, for example, incontrast to expiratory flow during exhalation. Accordingly, when manualventilations are detected, the system may sense when the patient is justbeginning a spontaneous inspiratory breath, and immediately prompt therescuer to administer a manual ventilation so that the positive pressurebreath is provided as air is being pulled into the lungs. This breathsynchronization protocol may be provided as a mode to the system, andrequires vigilance on the part of the system and the rescuer todetermine when a spontaneous breath is occurring. Or, the system mayfurther provide a notification to the rescuer of the effectiveness ofthe breath synchronization, particularly if the attempted breathsynchronization is ineffective or even harmful to the patient. If thebreath synchronization protocol is disabled, ventilation prompts may beprovided according to a timed rate such as in the case of a continuousbreath protocol, or ventilation prompts may be provided according to thenumber of chest compressions that have been administered; for example,based on the 30:2 protocol, the system may countdown the number of chestcompression that have occurred and prompt the rescuer to vent when thecountdown has finished.

As noted above, a number of treatment protocols may be employed formanually ventilating a patient, such as the 30:2 protocol, providing 2positive pressure breaths for 30 chest compressions. In this protocol,the system may display a ventilation dashboard (e.g., within an overallCPR dashboard, which may further include a chest compression dashboard,or simply having separate dashboards for ventilation and chestcompressions) that shows an indication of how many chest compressionsare remaining before a ventilation is to be administered. For example,as shown in FIG. 45(a), the dashboard may include a countdown bar thatdecrements with each detected chest compression. In this case, when achest compression is detected, the number of compressions remainingdecrements by 1 and the light-colored bar is slightly reduced in size.When the number of chest compressions reaches 0, or another value thatprovides an indication for a breath to be applied, the system promptsthe user to ventilate, as shown in FIG. 45(b). Or, in anotherembodiment, the dashboard may include a displayed number (e.g., numberprovided within a circled area), or other suitable indicator forcounting down to ventilation prompt.

For this manual ventilation technique, the dashboard further shows thevolume of air provided to the patient for a given bagged breath. Thedashboard depicted in FIG. 45(a) shows a numerical value of theventilation volume (shown as 500 mL) and a bar graph providing a visualindication of the ventilation volume. The bar graph includes hashmarkswhich indicate to the user the preferred range of volume per breath thatthe patient should receive. Any suitable upper and lower limits for thisrange may be chosen, depending on the desired volume to be administeredto the patient (e.g., 400 mL, 500 mL, 600 mL). In another embodiment, acircular region fills based on the detected flow volume and rate, andchanges color based on whether the volume and rate are or are not withindesired limits. For example, if the circular region turns green, thenflow volume and rate are within the prescribed range. If the circularregion turns yellow or red, then the flow volume is above, or below theprescribed range. An incomplete or partial filling of the circularregion may be an indication that the volume delivered is insufficient.In general, the ventilation breath should include a sufficient amount ofair to the lung that supplies enough of a source of oxygen for gasexchange and circulation to the body. Conversely, the ventilation breathshould not be excessive, otherwise lung damage may occur. The lowerlimit for the volume per breath given to the patient may beapproximately 100 mL, approximately 200 mL, approximately 250 L,approximately 300 mL, approximately 350 L, approximately 400 mL, etc.;conversely, the upper limit for the volume per breath given to thepatient may be approximately 1500 mL, approximately 1200 mL,approximately 1000 mL, approximately 900 mL, approximately 800 mL,approximately 750 mL, approximately 700 mL, approximately 650 L,approximately 600 mL, etc. The desired ventilation volume may depend onpatient characteristics, such as patient size, condition, age, weight,lung capacity, amongst others.

As noted above, the ventilation feedback provided may be customized forthe particular victim, or alternatively may follow a set (default)protocol that does not differ from victim to victim. For example, therate and volume of ventilation to provide a victim may depend on howlong the victim has been suffering from a current condition. Thus, arescuer may try to ascertain how long the victim has been down, or atime stamp from the time at which an emergency was called in may be usedas a proxy. Also, various states of the victim may be relevant to thetreatment protocol (e.g., rate and volume of ventilation) to be providedto the victim, including, for example, whether the patient is pediatricor adult; patient condition (e.g. traumatic brain injury, cerebralherniation, cardiac arrest); ECG characteristics that suggest differentventilation requirements (e.g., patients with ventricular fibrillationmay have lower ventilation requirements than patients with asystole orPEA; etiology of disease (e.g., cardiac arrest due to drowning vs.presumed myocardial infarction; duration of patient downtime for cardiacarrest; presence/absence of (effective) bystander CPR (compressionsand/or ventilations) prior to arrival of EMS; ETC02 levels (e.g.,recommendations to titrate ventilation rate to achieve a particular endtidal CO2 value; SpO2 levels (e.g., adjust ventilation rate to achieveoptimal peripheral oxygen saturation); and impact of SmO2 (muscleoxygenation) and/or tissue pH levels. Depending on what input parametersare provided to the system, an appropriate treatment protocol may beselected and/or adjusted, and ultimately communicated to the user.Though, in certain situations, such as those where the patient conditionis rapidly deteriorating (e.g., sudden oxygen desaturation, patientbecomes extremely hypotensive, etc.) it may be preferable that anychanges in protocol not be displayed or otherwise communicated to theuser, e.g., it may be better to maintain the current the current targetventilation parameters, rather than adjusting them.

When a positive pressure breath is provided, the bar graph on thedashboard may fill so as to show the instantaneous volume of airprovided to the patient. Hence, a manual bagger may view the bar graphto determine whether the total volume administered to the patient iswithin desired limits. As shown in FIG. 45(a), the 500 mL ventilationvolume falls within the specified limits. As also shown, when thepositive pressure breath is completed and chest compressions are to beadministered, the ventilation dashboard may continue to show informationregarding the previously provided ventilation breath during the currentset of chest compressions, until the next ventilation breath isadministered. The user should then provide a positive pressure breathsimilar to the previous breath. As further shown in FIG. 45(b), when thedashboard prompts the user to ventilate, the volume indication(numerical value and bar graph) resets and provides the ventilationvolume when the breath is applied. FIG. 45(c) shows the ventilationvolume to be 800 mL, which falls outside of the specified range.Accordingly, the dashboard provides an indication to the user that thepatient has been overventilated. This may provide a signal to the userto lessen the ventilation volume of the next positive pressure breath.

FIGS. 46(a)-(c) show a ventilation dashboard appropriate for acontinuous ventilation protocol, which may involve providing a breathprompt every 6-8 seconds during CPR. In this protocol, the ventilationdashboard may show an indication of how much time is left a ventilationis to be administered. For example, as shown in FIG. 46(a), thedashboard may include a countdown bar by seconds, with the light-coloredbar steadily or discretely decreasing in size, until it reaches 0, andthe user is then prompted to ventilate. The dashboard further showsrelevant information, such as the numeric ventilation volume and rate inbreaths per minute, from which the minute volume may be determined.Similar to the bar graph for ventilation volume, the bar graphcorresponding to ventilation rate includes hashmarks which indicate tothe user the preferred range of rate in breaths per minute that thepatient should receive. Appropriate upper and lower limits for thisrange may be chosen, depending on the desired ventilation rate (e.g., 6bpm, 8 bpm, 10 bpm). The lower limit for the rate given to the patientmay be approximately 4 bpm, approximately 6 bpm, approximately 8 bpm,approximately 10 bpm, etc.; conversely, the upper limit for the rategiven to the patient may be approximately 16 bpm, approximately 15 bpm,approximately 14 bpm, approximately 12 bpm, approximately 10 bpm,approximately 8 bpm, etc.

FIGS. 46(a) and 46(b) show the ventilation volume and rate to fallwithin specified limits. Though, FIG. 46(c) shows the ventilation rateto be 30 bpm, which falls outside of the specified range. Hence, thedashboard provides an indication to the user that the patient has beenoverventilated. This may provide a signal to the user to lessen the rateat which positive pressure breaths are given to the patient.

FIGS. 47(a) and 47(b) show similar information as that provided abovewith respect to ventilation volume, breath rate and countdowninformation to the next breath, with the addition of an option tomanually adjust the target parameters. As shown in these figures, thetarget rate may be adjusted, for example via touch screen interface onthe dashboard. While not shown, other parameters may also be adjusted,for example, the target ventilation volume and the limits for rate andvolume. In some cases, the size of the target range may be set such thatwhen a specified target volume or rate is input, the upper and lowerlimits (e.g., shown as hashmarks) adjust accordingly. Or, the individualupper and lower limits may be adjusted independently of one another.

FIG. 48 shows another embodiment that provides exemplary information,e.g., a ventilation timer 500, displayed on a display device to arescuer during the administration of ventilation to a patient. Theventilation timer 500 provides information to the rescuer to help therescuer control the rate of ventilation provided to the patient. Theventilation timer 500 can include a bar 506 (or other shape) that fillsas time elapses between breaths. The bar 506 can include scalinginformation (e.g., tick marks on the graph) that provide informationabout the elapsed time 502 and/or ventilation rate 504. The elapsed time502 provides an indication of the amount of time that has passed sincethe last ventilation event and the ventilation rate 504 provides thenumber of breaths per minute (e.g., 5 seconds between breaths=12breaths/minute).

The information displayed on the ventilation timer 500 is based onventilation related data received from a device that detects when aventilation has been delivered (e.g., a flow meter, capnography,thoracic impedance). The ventilation related information is used by acomputer to provide an input indicating when to re-start the timer suchthat the elapsed time can be determined.

In some examples, the information presented on the ventilation timer 500can be color coded or otherwise supplemented by a visual indicator ofranges that indicate adequate ventilation versus sub-optimalventilation. In one example, the color of the bar 506 in the ventilationtimer can change based on the adequacy of the ventilation. For example,the bar could be colored green when proper ventilation is being providedand yellow or red when the ventilation falls outside the desired rangeof respiration rates. Additionally, in some examples, an indication ofwhether the user should increase or decrease the rate of respirationcould be provided. Additionally, in some examples, an indication of theoptimal elapsed time/ventilation rate could be provided such as byoverlaying a line or other indicator at the desired level so the rescuercan attempt to have the bar 506 match the displayed optimal timingindicator.

In some additional examples, the information presented in theventilation timer 500 can be color coded or otherwise supplemented byother visual indicator based on the nature of the underlying conditionbeing treated, e.g. respiratory distress vs cardiac arrest vs TBI.Additionally, the range that is indicated as an optimal or an acceptablerespiration rate can change based on information from one or morephysiologic monitoring sensors and estimate from those sensor(s) of theunderlying status of the patient's cardiopulmonary status. Suchphysiologic monitoring can be based, for example on information aboutEtCO2 (e.g., the partial pressure or maximal concentration of carbondioxide, CO2 at the end of an exhaled breath, which is expressed as apercentage of CO2 or mmHg) and/or information about oxygen saturationfrom a pulse oximeter, a medical device that indirectly monitors theoxygen saturation of a patient's blood. Such physiologic monitoring canalso include information from a tissue CO2 sensor that can be used tocalculate the blood oxygen concentration, for example, based on theventilation/perfusion ratio (or V/Q ratio) which provides a measurementused to assess the efficiency and adequacy of the matching of the amountair reaching the alveoli to the amount of blood reaching the alveoli(sometimes reported as the VQ mismatch which is used to express when theventilation and the perfusion of a gas exchanging unit are not matched).

Minute-volume CO2 measures may be helpful during ventilation becauseETC02 measures are dependent on the actual volume of gas delivered tothe patient. The physiologic measure that the clinician is titrating tois the amount of CO2 gas exhaled from the patient, which is a helpfuloverall measure of the patient's physiologic state. Increasing theventilation rate or tidal volume will cause ETCO2 values to decrease fora fixed CO2 gas elimination rate from a patient; this is not the casefor minute-volume CO2 measures. Thus, minute-volume measures of CO2 maybe a useful parameter in situations where ventilation is being deliveredin a manual fashion with a rescuer squeezing a ventilation bag whereboth ventilation rates and tidal volumes have been shown in multiplestudies to be completely uncontrolled in the clinical environment.

CO2 concentration as a function of expired volume may be plotted such asin the form of a single-breath CO2 analysis (SBCO2), known to thoseskilled in the art. The SBCO2 curve has three phases: phase 1 made up ofnon-alveolar gas, or ventilatory dead-space gas, that is essentiallyfree of CO2; phase 2 that is a transition phase with a characteristicS-shape that contains some amount CO2; and phase 3 that is the alveolargas bearing the predominant quantity of exhaled CO2. Because the x-axisof the SBCO2, or expirogram as it is sometimes called, has units ofvolume, calculations can be made to determine both alveolar as well asnon-alveolar deadspace based on techniques known to those skilled in theart. For example, FIGS. 49(a) and 49(b) (from IEEE TRANSACTIONS ONINFORMATION TECHNOLOGY IN BIOMEDICINE, VOL. 6, NO. 4, DECEMBER 2002),each show the expired CO2 tension versus exhaled volume. Thenon-alveolar deadspace is the area of ‘Z’ in FIG. 49(a), and thealveolar deadspace is the area of ‘Y’. The sum of these two deadspacesdoes not produce any gas exchange in the patient, so this sets theminimum ventilation volume for each patient. Additionally, includingdynamic lung compliance in the calculation of overall lung volume usingSBCO2 curves may enhance the accuracy produced by SBCO2-basedcalculations.

FIG. 50 is an exemplary graph 910 of pressure 912 versus volume 914during manual ventilation. Indications of pressure versus volume can beused as a guide for determining an optimal tidal volume for manualventilation of victims. In general, for adult patients and olderchildren tidal volume (Vt) is calculated in milliliters per kilogram andvalues in the range of 6 to 8 mL/kg are often used. Hence a patientweighing 70 kg would get a Vt of 420-480 mL. However, in the field, arescuer often will not have access to patient weight to calculate adesired tidal volume. Thus, it can be beneficial to provide feedback tothe rescuer on an appropriate tidal volume without performingcalculations based on patient specific weight or age parameters.

In some cases, the height may be used as an estimate for weight and/orsize of the patient. For example, Broselow pediatric emergency tape maybe used as such as estimator. Broselow tape, generally speaking, has ascale provided as a color-coded measure for pediatric emergencies. TheBroselow scale relates the height of a child (up to approximately 12years in age) as measured by the tape to his/her weight (up toapproximately 36 kg or 80 lbs), which is useful to provide medicaltreatment instructions, such as medication dosages, the size of theequipment that should be used, the level of defibrillation shockvoltage, amongst others. Particular to children is the need to calculatethe relevant therapies for each child individually, primarily based onsize. And in an emergency, the time required to make such calculation(s)may detract from valuable time needed to evaluate, initiate, and monitorpatient treatment. A similar Broselow-type scale may be used todetermine the ventilation parameters that would apply for pediatric oradult patients. That is, ventilation parameters may vary based on thesize of the patient, whether pediatric or adult. For example, theestimated tidal volume, breath volume/rate, etc. may be provided astargets to the rescuer administering the therapy. Tidal volume maygenerally be determined based on predicted body weight (not necessarilyactual body weight because overweight people generally have similarlysized lungs as thinner people of the same height), estimated from genderand height. For example, the predicted body weight (kg) for females isgenerally (50+2.3 (height (in)−60); and for males is generally (45.5+2.3(height (in)−60). In some embodiments, the system may be configured toestimate size/weight of the patient and, hence, select an appropriatetherapy based on an input (e.g., via a user interface) of patient heightor other size information. The feedback information provided to therescuer may then be adjusted based on the selected therapy.

In manual ventilation, as shown in FIG. 50, as the volume 914 of airadministered to the victim increases, initially the pressure remains lowand substantially constant (portion 916) as the lungs inflate. As thelungs near full inflation, the pressure required to administeradditional volume is increased (portion 918). As the pressure risesabove 45 cm H2O (4.4 kPa) for adults, the risk of barotrauma isincreased and efforts should be made to try to reduce the peak airwaypressure. In infants and children, even lower levels of peak pressuremay cause damage. In general, keeping peak pressures below 30 cm H2O(2.9 kPa) (denoted by line 920) may be desirable. Thus, by observingchanges in the peak pressure or by observing changes in pressure perchanges in volume, a determination can be made of when a desirable tidalvolume has been administered to the victim.

The change in volume divided by change in pressure is sometimes referredto as a compliance measurement. Compliance is a measure of the“stiffness” of the lung and chest wall. The mathematical formula forcompliance (C) is change in volume divided by change in pressure. Thehigher the compliance, the more easily the lungs will inflate inresponse to positive pressure. Compliance values can be calculated andused to provide feedback on tidal volume to the rescuer.

The ventilation dashboard may be provided as a standalone display or asa portion of a CPR dashboard or larger display, for example, on the userinterface display of a hospital or EMS monitor, such as the E Series®, MSeries®, R Series® and X Series®, provided by ZOLL Medical Corporation.The ventilation and CPR dashboard may also be provided as part ofdisplays described in U.S. Pat. No. 8,725,253, entitled “DefibrillatorDisplay Including CPR Depth Information,” which is hereby incorporatedby reference in its entirety.

For example, a general display may include a wide variety ofphysiological data of the patient, such as ECG, EtCO2, SpO2, bloodpressure, muscle oxygenation, muscle pH, diagnostic information, heartrate, temperature, etc. The general display may also include a CPRdashboard, which may provide the user with resuscitative informationuseful for assisting a user in providing resuscitative treatment to thepatient, for example, in maintaining the quality of CPR, including chestcompressions and/or ventilations. Accordingly, the CPR dashboard mayinclude a chest compression dashboard, for tracking parameters usefulfor providing quality chest compressions, such as depth, rate and/orrelease. The CPR dashboard may also include a ventilation dashboard, fortracking parameters useful for providing quality ventilations, such asventilation rate, volume, minute volume and/or ventilation timing.

Other resuscitative information for assisting the user in providingresuscitative treatment may be provided, for example, based on a numberof embodiments described herein. For instance, such resuscitativeinformation may include feedback for instructing a user to adjust gasflow (e.g., flow rate, flow volume, minute volume) through the lumen,feedback for instructing a user to adjust placement of an intubationtube, alerts to a user and/or machine that overventilation has occurredor may occur, a countdown of the number of chest compressions until asubsequent ventilation is to be applied, a countdown of the time until asubsequent ventilation is to be applied, a number of chest compressionsapplied based on pressure and/or flow rate signals, a determination ofwhether a detected breath is due to spontaneous breathing, manuallyapplied ventilation or automatically applied ventilation, instructionsto the user to check the patient based on an indication of whether ROSCmay have occurred, an indication of the determined peak inspiratorypressure, flow rate and/or volume of gas flowing through the lumen ofthe flow conduit, amongst others in accordance with embodimentsdiscussed herein.

The physiological data of the patient and the resuscitative informationmay be provided on a display interface of a defibrillator and/ormonitor. In some embodiments, the physiological data of the patient maybe provided on a first portion of the display and the resuscitativeinformation of assisting the user in providing resuscitative treatmentmay be provided on a second portion of the display. That is, dependingon what information may be most relevant in treating the patient, thedisplay may provide both physiological data of the patient andresuscitative information for assisting the user.

FIGS. 51-53 also show various embodiments of screen shots of suchdisplays, each of which includes additional information other than theCPR dashboard (which may include a chest compression dashboard and/orventilation dashboard), such as physiological data, for example, theheart rate, blood pressure, ETCO2, SpO2, temperature, etc. The CPRdashboard may include a chest compression dashboard providing feedbackon the depth, rate, release of chest compressions, and/or a ventilationdashboard, which shows the breath volume, breath rate, minute volume anda countdown to when the patient should be ventilated.

The display interface of FIG. 51 depicts the CPR dashboard and a graphshowing trends in flow volume over time, as provided via the flow sensorsystem. This CPR dashboard may be relevant for a patient suffering fromcardiac arrest, where both chest compressions and ventilations areprovided. This display interface further shows other physiological data,including ECG data, heart rate, NIBP, EtCO2, SpO2 and temperature of thepatient.

The ventilation portion of the CPR dashboard of FIG. 52 shows the breathvolume and rate to have exceeded their preferred ranges, respectively,and so displays a message to the user that the patient has beenoverventilated. Similar to the embodiment of FIG. 51, this CPR dashboardmay also be relevant for a patient suffering from cardiac arrest. Thedisplay interface of FIG. 52 further shows other physiological data,such as ECG data, heart rate, NIBP, EtCO2, SpO2, a capnogram andtemperature of the patient.

FIG. 53 shows an example of a display interface including theventilation dashboard, without showing the chest compression portion ofthe CPR dashboard, which may be preferable for a patient experiencingrespiratory distress or traumatic brain injury, rather than cardiacarrest. That is, there is no need to provide chest compression feedbackif no chest compressions are being applied to the patient. The displayinterface of FIG. 53 further provides a graph that shows trends in flowvolume for each breath. As shown, each ventilation volume provided tothe patient is between 225 mL and 450 L. The display interface of FIG.53 also shows other physiological data, such as ECG data, heart rate,NIBP, EtCO2, SpO2 and temperature of the patient.

Similar to the above, FIGS. 63-66 depict additional embodiments ofscreen shots 1000 of a display monitor showing a variety ofresuscitation related data, including a ventilation dashboard. Thedisplay system may be configured such that when air flow is detectedthrough the sensor, the ventilation dashboard 1010 automatically appearsalong with ventilation history 1014, which provides a bar that shows theventilation volume at specific time points. As shown in FIGS. 63-66, theventilation dashboard 1010 includes a numerical ventilation volumeindicator 1011, a numerical ventilation rate indicator 1013 and aventilation performance indicator 1012. The display may also shownumerical values for inspiratory volume 1016 and expiratory volume 1018for each positive pressure breath ventilation.

In this embodiment, the ventilation performance indicator 1012 isprovided as a graphic of a circular region that fills as inspiratory airis detected by the flow sensor system. After the breath is over, thecircular region may change color depending on whether the ventilationrate or volume is within a pre-specified target range. For example, thecircular region may display a green color, or another appropriate color,if both the measured ventilation rate and volume fall within the targetrange. Though, if either of the ventilation volume or ventilation ratefalls outside of the target range, the circular region may display adifferent color, such as yellow, orange, red, or another color,indicating that one of more parameters are out of range. For example, ifthe patient is under-ventilated (i.e., given a volume lower than thelower bound of the target range) or over-ventilated (i.e., given avolume that exceeds the upper bound of the target range), then thecircular region of the ventilation performance indicator 1012 may depicta yellow warning color or other suitable color, and the numericalventilation volume indicator 1011 may also change to a similar color(e.g., yellow). Similarly, if the measured ventilation rate does notfall within the pre-specified target range, then the circular region ofthe ventilation performance indicator 1012 may illuminate a yellowwarning color or other suitable color, and the numerical ventilationrate indicator 1013 may also exhibit a similar change in color.

As shown in FIG. 63, the ventilation performance indicator 1012 mayinclude a numerical countdown timer located within the circular region.Once the numerical countdown timer counts down to 0 (e.g., counting downby seconds or another time period), then, as shown in FIG. 64, thecircular region empties and a “Ventilate” prompt 1020 appears. This isto instruct a user to apply a positive pressure ventilation to thepatient (e.g., by squeezing an attached bag valve mask). If no breath isdetected after a period of time (e.g., 3-5 seconds), then the“Ventilate” prompt 1020 begins to flash. If no breath is detected aftera subsequent period of time (e.g., another 3-5 seconds), then thecircular region itself flashes and optionally changes color to warn theuser that a ventilation should be given. Or, alarms (e.g., audible,visual, tactile) may be further triggered to warn the user that aventilation action should be taken. It can be appreciated that othermethods and displays for providing ventilation information and promptingto the user may be employed.

FIG. 65 illustrates a screen shot of the ventilation dashboard 1010along with a chest compression dashboard 1030, which provides chestcompression feedback for the user in compressing the chest within anappropriate target depth and rate. Similar to the ventilation historyindicator 1014, the chest compression history indicator 1034 shows a barfor the depth of each chest compression during a CPR interval.

FIG. 66 shows a screen shot of the ventilation dashboard 1010 along witha traumatic brain injury (TBI) dashboard 1040, which provides parametersuseful for monitoring a patient who has suffered from a traumatic braininjury. Accordingly, in addition to the ventilation dashboard 1010, theTBI dashboard 1040 includes trending graphs for NIBP, EtCO2 and SpO2over appropriate time intervals.

In some embodiments, the flow sensor system may report trends ofventilation volume and rate over time, which can provide signs ofincreasing difficulty of breathing for the patient or how the patient isresponding to treatment. For instance, such trends may assist indetermining whether the provided treatment is working. If, prior totreatment, the patient is experiencing rapid and shallow breathing, butafter treatment the metrics have improved to normal ranges, then it maybe determined that the treatment is working within desired parameters.If the trends remain unchanged, then this may indicate that eitheranother dose needs to be given to the patient or a different treatmentshould be provided. FIGS. 54 and 55 depict graphs that show examples ofthe ventilation volume over time and the ventilation rate over time,respectively. These values may be reported as averages over pre-set timeintervals (e.g., 30 seconds, 1 minute, 2 minutes, etc.).

In another embodiment of an interface display for use with flow sensorsystems described herein, an interactive tool may be used to aid inusers attempts to administer the proper volume of air to a patient atthe proper times and at the proper pressures. The interactive tool mayinvolve a simple graphical symbol, icon or other visual indicia,provided as a ventilation performance indicator, which varies over timein a manner that encourages the user to perform manual ventilationswithin preferred parameters. In this example, by responding to thechanging symbol, the user may be able to perform high quality therapy(e.g., manual ventilations) without having to know specific numbers orprotocols.

In certain embodiments, as shown in FIGS. 56(a)-(e), the graphic 1100used for helping to indicate the quality of ventilations may include asimple filled circle or any other suitable shape (e.g., square, polygon,ellipse, etc.) with a solid colored core region 1101 and a perimeter1102 of contrasting color that is easily seen. The perimeter 1102 of thecircle (or other shape) may provide a boundary that the user mayreference in administering manual ventilations to the patient. Forexample, as the user administers a ventilation breath, which adds volumeto the patient's lungs, the inner core region 1101 of the circle maybegin to fill up, and the boundary 1102 may provide a visual indicationof the preferred ventilation volume to the patient. In this regard,exceeding the boundary limit may be an indication to the user that thepatient is being overventilated.

As an example, when the interactive program for ventilation starts, theventilation performance indicator 1100 may be provided as a circle (orother intuitive shape) that is filled according with a certain color,indicating that the patient is not yet in need of ventilations. FIG.56(a) shows an example of the interactive tool in a rest state, wherethe administration of ventilations is not yet recommended. In somecases, when it is determined that the user should receive ventilations,the ventilation performance indicator 1100 may provide a visualcommunication of that determination to the user. For instance,immediately before the user is supposed to start applying air to thepatient (bagging), the filled core 1101 of the circle may change colors,as shown in FIG. 56(b), or may flash with a contrasting color, alertingthe user that they should apply bagging therapy. Other indications thatthe user should ventilate may be provided, for example, the graphic mayoptionally provide flashing or steady text (e.g., “ventilate”) inside oroutside the circle.

Upon the start of ventilation, as shown in FIG. 56(c), the entire core1101 of the circle (or other shape) is filled with an interactive(“living”) object 1103 having a third contrasting color that mayimmediately begin to shrink in size. FIG. 56(d) depicts an example ofthe interactively shrinking object 1103, which had previously filled theinner core 1101 of the circular outer boundary 1102. Depending on therecommended rate and volume of flow, this interactive object 1103 mayshrink at a rate that is intended to simulate the depletion of oxygenfrom the lungs. When an appropriate amount of air is provided to thepatient, the interactive object 1103 then increases in size (e.g.,radius); in this example, upon the application of each manual bagging,the radius of the interactive object increases toward the outer boundary1102 of the graphic.

Such an interactive tool provides an indication of ventilation qualityby effectively encouraging the person administering manual ventilationsto compensate for the shrinkage of the interactive object by squeezingor otherwise manipulating the bag in attempting to make the interactiveobject substantially match the shape of the outer boundary. Hence, inthis example of a circular ventilation performance indicator, theobjective of the user is to keep the circle full. The manner in whichthe size of the interactive object 1103 changes (e.g., decreasing due tooxygen depletion and increasing due to manual bagging) may be controlledby an algorithm that simulates gas exchange (e.g., oxygen and/or CO2exchange) and flow rate/volume. Thus, when oxygen is removed from thelungs and replaced with CO2, the interactive object 1103 may shrink insize, and when fresh air is provided to the lungs, the size of theinteractive object may increase.

When the size of the interactive object 1103 increases so as to exceedthe outer boundary 1102 of the graphic, it may be determined thatoverventilation may be occurring. FIG. 56(e) depicts an example wherethe graphic 1100 indicates the bagger to be overventilating, forexample, the size of the interactive object 1103 overflows past theouter boundary 1102. In some cases, if overventilation is detected, thecolor of the interactive object 1103 and/or a substantial portion of theentire graphical simulation 1100 may change, for example, to red oryellow, denoting to the user that ventilation flows are beyond specifiedparameters.

When manual ventilations are finished, the ventilation performanceindicator 1100 may return back to the rest state, for example, as shownin FIG. 56(a). When ventilations are to be administered again (e.g., asindicated by a countdown/count up timer and/or chest compressioncounter), the ventilation performance indicator 1100 may then activateso as to provide appropriate guidance to the user. This interactive toolmay be provided to the user as a simple game that assists the user todeliver appropriate quantities of air according to recommended times andrates. In certain embodiments, the objective of the game may be to “keepthe circle full.” While the user is presented with this simple task, inthe background, the system performs calculations and adjustments tocorrelate the behavior of the ventilation performance indicator,including the interactive object, with the rate volume of air to betherapeutically administered to the patient, at appropriate timingintervals.

Although a flow sensor system has been described in detail for thepurpose of illustration based on what is currently considered to be themost practical examples, it is to be understood that such detail issolely for that purpose and that the subject matter of this disclosureis not limited to the disclosed examples, but, on the contrary, isintended to cover modifications and equivalent arrangements. Forexample, it is to be understood that this disclosure contemplates that,to the extent possible, one or more features of any example can becombined with one or more features of any other example.

As used herein, the singular form of “a”, “an”, and “the” include pluralreferents unless the context clearly dictates otherwise.

As used herein, the terms “right”, “left”, “top”, “bottom”, andderivatives thereof shall relate to the subject matter of thisdisclosure as it is oriented in the drawing figures. However, it is tobe understood that the subject matter of this disclosure can assumevarious alternative orientations and, accordingly, such terms are not tobe considered as limiting. Also, it is to be understood that the subjectmatter of this disclosure can assume various alternative variations andstage sequences, except where expressly specified to the contrary. It isalso to be understood that the specific devices and processesillustrated in the attached drawings, and described in the followingspecification, are examples. Hence, specific dimensions and otherphysical characteristics related to the embodiments disclosed herein arenot to be considered as limiting.

1. A flow sensor system for assisting resuscitative treatment,comprising: a flow conduit configured to be placed in a patient airwayand having a lumen that accommodates gas flow between a first region anda second region; a flow restrictor disposed within the lumen of the flowconduit between the first region and the second region; and at least onepressure sensor configured to measure gas pressure of at least one ofthe first region and the second region of the flow conduit, wherein asensitive region of the flow sensor system exhibits a greater level ofhydrophobicity than a neighboring region adjacent to the sensitiveregion. 2-3. (canceled)
 4. The flow sensor system according to claim 1,wherein the neighboring region includes a reservoir configured tocollect water arising from gas flowing through the lumen.
 5. The flowsensor system according to claim 1, wherein the neighboring region isconfigured to wick away water from the sensitive region.
 6. The flowsensor system according to claim 1, wherein the at least one pressuresensor includes a first absolute pressure sensor configured to measuregas pressure at the first region of the flow conduit and a secondabsolute pressure sensor configured to measure gas pressure at thesecond region of the flow conduit.
 7. The flow sensor system accordingto claim 1, wherein the at least one pressure sensor includes adifferential pressure sensor configured to measure differential gaspressure between the first and second regions of the flow conduit. 8.The flow sensor system according to claim 1, further comprising aprocessor in communication with the at least one pressure sensor, theprocessor being configured to analyze the measured gas pressure of atleast one of the first region and the second region of the flow conduitand generate a signal indicative of at least one of a peak inspiratorypressure, a flow rate and a volume of gas flowing through the lumen ofthe flow conduit based on the pressure measurements in the first andsecond regions of the flow conduit.
 9. (canceled)
 10. The flow sensorsystem according to claim 8, further comprising a feedback device,wherein the processor is configured to send a feedback signal to thefeedback device to provide resuscitative information based on at leastone of peak inspiratory pressure, the determined flow rate and thedetermined volume of gas flowing through the lumen.
 11. The flow sensorsystem according to claim 10, wherein the resuscitative informationincludes at least one of feedback for instructing a user to adjustplacement of an intubation tube, an alert that overventilation hasoccurred, a countdown of at least one of a number of chest compressionsand time until a subsequent ventilation is to be applied, a number ofchest compressions applied based on at least one of the first and secondsignals, a determination of whether a detected breath is due tospontaneous breathing, manually applied ventilation or automaticallyapplied ventilation, an indication of whether ROSC may have occurred,and at least one of the determined peak inspiratory pressure, flow rateand volume of gas flowing through the lumen of the flow conduit. 12-14.(canceled)
 15. The flow sensor system according to claim 8, furthercomprising a connector removably coupled with the flow conduit, theconnector being configured to place the at least one pressure sensor incommunication with the processor. 16-19. (canceled)
 20. The flow sensorsystem according to claim 8, wherein the flow restrictor is configuredto interrupt the flow of gas through the lumen to create a pressure dropin the lumen between the first region and the second region and theprocessor is configured to determine the pressure drop based on thepressure measurements of the at least one pressure sensor and todetermine at least one of the flow rate, a direction of flow and volumeof gas flowing through the lumen based on the determined pressure drop.21-30. (canceled)
 31. The flow sensor system according to claim 1,further comprising a circuit board disposed on the flow conduit, the atleast one pressure sensor being connected to the circuit board, whereinthe circuit board comprises at least one heating element configured tobe energized to prevent or limit fluid accumulation near the at leastone pressure sensor. 32-44. (canceled)
 45. The flow sensor systemaccording to claim 1, wherein the flow conduit comprises a bodyextending from a first end to a second end, the body of the flow conduithaving a hollow interior defining the lumen for the gas flow, andwherein the body of the flow conduit comprises at least one chamberconfigured to house and support the at least one pressure sensor. 46.(canceled)
 47. The flow sensor system according to claim 45, wherein theat least one chamber includes a first chamber and a second chamber inseparate fluid communication with the lumen via respective openingsdefined in the body of the flow conduit.
 48. The flow sensor systemaccording to claim 45, further comprising at least one barrier forprotecting the at least one chamber.
 49. The flow sensor systemaccording to claim 48, wherein the at least one barrier is configured toallow passage of gas and obstruct passage of moisture and debristherethrough. 50-132. (canceled)
 133. A flow sensor system forventilation treatment, comprising: a flow conduit configured to allowgas flow between a first region and a second region, the flow conduitdefining a lumen for the gas flow; a flow restrictor disposed within thelumen of the flow conduit between the first region and the secondregion; and at least one absolute pressure sensor configured to measurepressure of the gas flow at at least one of the first region and thesecond region of the flow conduit. 134-136. (canceled)
 137. The flowsensor system according to claim 133, wherein a sensitive region of theflow sensor system exhibits a greater level of hydrophobicity than aneighboring region adjacent to the sensitive region.
 138. The flowsensor system according to claim 133, wherein the at least one absolutepressure sensor includes a first absolute pressure sensor configured tomeasure gas pressure at the first region of the flow conduit and asecond absolute pressure sensor configured to measure gas pressure atthe second region of the flow conduit.
 139. The flow sensor systemaccording to claim 133, further comprising a processor in communicationwith the at least one pressure sensor, the processor being configured toanalyze the measured gas pressure of at least one of the first regionand the second region of the flow conduit and generate a signalindicative of at least one of a peak inspiratory pressure, a flow rateand a volume of gas flowing through the lumen of the flow conduit basedon the pressure measurements in the first and second regions of the flowconduit.
 140. The flow sensor system according to claim 139, furthercomprising a feedback device, wherein the processor is configured tosend a feedback signal to the feedback device to provide resuscitativeinformation based on at least one of peak inspiratory pressure, thedetermined flow rate and the determined volume of gas flowing throughthe lumen.
 141. The flow sensor system according to claim 140, whereinthe resuscitative information includes at least one of feedback forinstructing a user to adjust placement of an intubation tube, an alertthat overventilation has occurred, a countdown of at least one of anumber of chest compressions and time until a subsequent ventilation isto be applied, a number of chest compressions applied based on at leastone of the first and second signals, a determination of whether adetected breath is due to spontaneous breathing, manually appliedventilation or automatically applied ventilation, an indication ofwhether ROSC may have occurred, and at least one of the determined peakinspiratory pressure, flow rate and volume of gas flowing through thelumen of the flow conduit.
 142. The flow sensor system according toclaim 139, further comprising a connector removably coupled with theflow conduit, the connector being configured to place the at least onepressure sensor in communication with the processor.
 143. The flowsensor system according to claim 139, wherein the flow restrictor isconfigured to interrupt the flow of gas through the lumen to create apressure drop in the lumen between the first region and the secondregion and the processor is configured to determine the pressure dropbased on the pressure measurements of the at least one absolute pressuresensor and to determine at least one of the flow rate, a direction offlow and volume of gas flowing through the lumen based on the determinedpressure drop.
 144. The flow sensor system according to claim 133,further comprising a circuit board disposed on the flow conduit, the atleast one absolute pressure sensor being connected to the circuit board,and wherein the circuit board comprises at least one heating elementconfigured to be energized to prevent or limit fluid accumulation nearthe at least one absolute pressure sensor.
 145. The flow sensor systemaccording to claim 133, wherein the flow conduit comprises a bodyextending from a first end to a second end, the body of the flow conduithaving a hollow interior defining the lumen for the gas flow, andwherein the body of the flow conduit comprises at least one chamberconfigured to house and support the at least one pressure sensor. 146.The flow sensor system according to claim 145, wherein the at least onechamber includes a first chamber and a second chamber in separate fluidcommunication with the lumen via respective openings defined in the bodyof the flow conduit.
 147. The flow sensor system according to claim 145,further comprising at least one barrier for protecting the at least onechamber.
 148. The flow sensor system according to claim 147, wherein theat least one barrier is configured to allow passage of gas and obstructpassage of moisture and debris therethrough.